Consciousness is the state or quality of awareness or of being aware of an external object or something within oneself. It has been defined variously in terms of sentience, qualia, the ability to experience or to feel, having a sense of selfhood or soul, the fact that there is something "that it is like" to "have" or "be" it, the executive control system of the mind. Despite the difficulty in definition, many philosophers believe that there is a broadly shared underlying intuition about what consciousness is; as Max Velmans and Susan Schneider wrote in The Blackwell Companion to Consciousness: "Anything that we are aware of at a given moment forms part of our consciousness, making conscious experience at once the most familiar and most mysterious aspect of our lives."Western philosophers, since the time of Descartes and Locke, have struggled to comprehend the nature of consciousness and identify its essential properties. Issues of concern in the philosophy of consciousness include whether the concept is fundamentally coherent.
Thanks to developments in technology over the past few decades, consciousness has become a significant topic of interdisciplinary research in cognitive science, with significant contributions from fields such as psychology, anthropology and neuroscience. The primary focus is on understanding what it means biologically and psychologically for information to be present in consciousness—that is, on determining the neural and psychological correlates of consciousness; the majority of experimental studies assess consciousness in humans by asking subjects for a verbal report of their experiences. Issues of interest include phenomena such as subliminal perception, denial of impairment, altered states of consciousness produced by alcohol and other drugs, or spiritual or meditative techniques. In medicine, consciousness is assessed by observing a patient's arousal and responsiveness, can be seen as a continuum of states ranging from full alertness and comprehension, through disorientation, loss of meaningful communication, loss of movement in response to painful stimuli.
Issues of practical concern include how the presence of consciousness can be assessed in ill, comatose, or anesthetized people, how to treat conditions in which consciousness is impaired or disrupted. The degree of consciousness is measured by standardized behavior observation scales such as the Glasgow Coma Scale; the origin of the modern concept of consciousness is attributed to John Locke's Essay Concerning Human Understanding, published in 1690. Locke defined consciousness as "the perception of what passes in a man's own mind", his essay influenced the 18th-century view of consciousness, his definition appeared in Samuel Johnson's celebrated Dictionary. "Consciousness" is defined in the 1753 volume of Diderot and d'Alembert's Encyclopédie, as "the opinion or internal feeling that we ourselves have from what we do." The earliest English language uses of "conscious" and "consciousness" date back, however, to the 1500s. The English word "conscious" derived from the Latin conscius, but the Latin word did not have the same meaning as our word—it meant "knowing with", in other words "having joint or common knowledge with another".
There were, many occurrences in Latin writings of the phrase conscius sibi, which translates as "knowing with oneself", or in other words "sharing knowledge with oneself about something". This phrase had the figurative meaning of "knowing that one knows", as the modern English word "conscious" does. In its earliest uses in the 1500s, the English word "conscious" retained the meaning of the Latin conscius. For example, Thomas Hobbes in Leviathan wrote: "Where two, or more men, know of one and the same fact, they are said to be Conscious of it one to another." The Latin phrase conscius sibi, whose meaning was more related to the current concept of consciousness, was rendered in English as "conscious to oneself" or "conscious unto oneself". For example, Archbishop Ussher wrote in 1613 of "being so conscious unto myself of my great weakness". Locke's definition from 1690 illustrates. A related word was conscientia, which means moral conscience. In the literal sense, "conscientia" means knowledge-with, that is, shared knowledge.
The word first appears in Latin juridical texts by writers such as Cicero. Here, conscientia is the knowledge. René Descartes is taken to be the first philosopher to use conscientia in a way that does not fit this traditional meaning. Descartes used conscientia the way modern speakers would use "conscience". In Search after Truth he says "conscience or internal testimony"; the dictionary meanings of the word consciousness extend through several centuries and several associated related meanings. These have ranged from formal definitions to definitions attempting to capture the less captured and more debated meanings and usage of the wor
Philosophy of mind
Philosophy of mind is a branch of philosophy that studies the ontology and relationship of the mind to the body. The mind–body problem is a paradigm issue in philosophy of mind, although other issues are addressed, such as the hard problem of consciousness, the nature of particular mental states. Aspects of the mind that are studied include mental events, mental functions, mental properties, the ontology of the mind, the nature of thought, the relationship of the mind to the body. Dualism and monism are the two central schools of thought on the mind–body problem, although nuanced views have arisen that do not fit one or the other category neatly. Dualism finds its entry into Western philosophy thanks to René Descartes in the 17th century. Substance dualists like Descartes argue that the mind is an independently existing substance, whereas property dualists maintain that the mind is a group of independent properties that emerge from and cannot be reduced to the brain, but that it is not a distinct substance.
Monism is the position that body are not ontologically distinct entities. This view was first advocated in Western philosophy by Parmenides in the 5th century BCE and was espoused by the 17th-century rationalist Baruch Spinoza. Physicalists argue that only entities postulated by physical theory exist, that mental processes will be explained in terms of these entities as physical theory continues to evolve. Physicalists maintain various positions on the prospects of reducing mental properties to physical properties, the ontological status of such mental properties remains unclear. Idealists maintain that the mind is all that exists and that the external world is either mental itself, or an illusion created by the mind. Neutral monists such as Ernst Mach and William James argue that events in the world can be thought of as either mental or physical depending on the network of relationships into which they enter, dual-aspect monists such as Spinoza adhere to the position that there is some other, neutral substance, that both matter and mind are properties of this unknown substance.
The most common monisms in the 20th and 21st centuries have all been variations of physicalism. Most modern philosophers of mind adopt either a reductive physicalist or non-reductive physicalist position, maintaining in their different ways that the mind is not something separate from the body; these approaches have been influential in the sciences in the fields of sociobiology, computer science, evolutionary psychology and the various neurosciences. Reductive physicalists assert that all mental states and properties will be explained by scientific accounts of physiological processes and states. Non-reductive physicalists argue that although the mind is not a separate substance, mental properties supervene on physical properties, or that the predicates and vocabulary used in mental descriptions and explanations are indispensable, cannot be reduced to the language and lower-level explanations of physical science. Continued neuroscientific progress has helped to clarify some of these issues. Modern philosophers of mind continue to ask how the subjective qualities and the intentionality of mental states and properties can be explained in naturalistic terms.
The mind–body problem concerns the explanation of the relationship that exists between minds, or mental processes, bodily states or processes. The main aim of philosophers working in this area is to determine the nature of the mind and mental states/processes, how—or if—minds are affected by and can affect the body. Our perceptual experiences depend on stimuli that arrive at our various sensory organs from the external world, these stimuli cause changes in our mental states causing us to feel a sensation, which may be pleasant or unpleasant. Someone's desire for a slice of pizza, for example, will tend to cause that person to move his or her body in a specific manner and in a specific direction to obtain what he or she wants; the question is how it can be possible for conscious experiences to arise out of a lump of gray matter endowed with nothing but electrochemical properties. A related problem is how someone's propositional attitudes cause that individual's neurons to fire and muscles to contract.
These comprise some of the puzzles that have confronted epistemologists and philosophers of mind from at least the time of René Descartes. Dualism is a set of views about the relationship between matter, it begins with the claim. One of the earliest known formulations of mind–body dualism was expressed in the eastern Sankhya and Yoga schools of Hindu philosophy, which divided the world into purusha and prakriti; the Yoga Sutra of Patanjali presents an analytical approach to the nature of the mind. In Western Philosophy, the earliest discussions of dualist ideas are in the writings of Plato who maintained that humans' "intelligence" could not be identified with, or explained in terms of, their physical body. However, the best-known version of dualism is due to René Descartes, holds that the mind is a non-extended, non-physical substance, a "res cogitans". Descartes was the first to identify the mind with consciousness and self-awareness, to distinguish this from the brain, the seat of intelligence.
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Solipsism is the philosophical idea that only one's own mind is sure to exist. As an epistemological position, solipsism holds that knowledge of anything outside one's own mind is unsure; as a metaphysical position, solipsism goes further to the conclusion that the world and other minds do not exist. This extreme position is claimed to be irrefutable, as the solipsist believes themself to be the only true authority, all others being creations of their own mind. There are varying degrees of solipsism that parallel the varying degrees of skepticism: Metaphysical solipsism is a variety of solipsism. Based on a philosophy of subjective idealism, metaphysical solipsists maintain that the self is the only existing reality and that all other realities, including the external world and other persons, are representations of that self, have no independent existence. There are several versions of metaphysical solipsism, such as Caspar Hare's egocentric presentism, in which other people are conscious, but their experiences are not present.
Epistemological solipsism is the variety of idealism according to which only the directly accessible mental contents of the solipsistic philosopher can be known. The existence of an external world is regarded as an unresolvable question rather than false. Further, one cannot be certain as to what extent the external world exists independently of one's mind. For instance, it may be that a God-like being controls the sensations received by one's brain, making it appear as if there is an external world when most of it is false. However, the point remains. Methodological solipsism is an agnostic variant of solipsism, it exists in opposition to the strict epistemological requirements for "knowledge". It still entertains the points. Methodological solipsism sometimes goes further to say that what we perceive as the brain is part of the external world, for it is only through our senses that we can see or feel the mind. Only the existence of thoughts is known for certain. Methodological solipsists do not intend to conclude that the stronger forms of solipsism are true.
They emphasize that justifications of an external world must be founded on indisputable facts about their own consciousness. The methodological solipsist believes that subjective impressions or innate knowledge are the sole possible or proper starting point for philosophical construction. Methodological solipsism is not held as a belief system, but rather used as a thought experiment to assist skepticism. Denial of material existence, in itself, does not constitute solipsism. A feature of the metaphysical solipsistic worldview is the denial of the existence of other minds. Since personal experiences are private and ineffable, another being's experience can be known only by analogy. Philosophers try to build knowledge on more than an analogy; the failure of Descartes' epistemological enterprise brought to popularity the idea that all certain knowledge may go no further than "I think. The theory of solipsism merits close examination because it relates to three held philosophical presuppositions, each itself fundamental and wide-ranging in importance: My most certain knowledge is the content of my own mind—my thoughts, affects, etc.
There is no conceptual or logically necessary link between mental and physical—between, the occurrence of certain conscious experience or mental states and the'possession' and behavioral dispositions of a'body' of a particular kind. The experience of a given person is private to that person. To expand on point 2 a little further, the conceptual problem here is that the previous assumes mind or consciousness can exist independent of some entity having this capability, i.e. that an attribute of an existent can exist apart from the existent itself. If one admits to the existence of an independent entity having that attribute, the door is open; some people hold that, while it cannot be proven that anything independent of one's mind exists, the point that solipsism makes is irrelevant. This is because, whether the world as we perceive it exists independently or not, we cannot escape this perception, hence it is best to act assuming that the world is independent of our minds. For example, if one committed a crime, one is to be punished, causing potential distress to oneself if the world was not independent of one's mind.
There is the issue of plausibility to consider. If one is the only mind in existence one is maintaining that one's mind alone created all of which one is aware; this includes the symphonies of Beethoven, the works of Shakespeare, all of mathematics and science, etc. Critics of solipsism find this somewhat implausible. However, for example, people are able to construct entire worlds inside their minds while having dreams when asleep, people have had dreams which included things such as music of Beethoven or the works of Shakespeare or math or science in them, solipsists do have coun
Mind–body dualism, or mind–body duality, is a view in the philosophy of mind that mental phenomena are, in some respects, non-physical, or that the mind and body are distinct and separable. Thus, it encompasses a set of views about the relationship between mind and matter, between subject and object, is contrasted with other positions, such as physicalism and enactivism, in the mind–body problem. Aristotle shared Plato's view of multiple souls and further elaborated a hierarchical arrangement, corresponding to the distinctive functions of plants and people: a nutritive soul of growth and metabolism that all three share. In this view, a soul is the hylomorphic form of a viable organism, wherein each level of the hierarchy formally supervenes upon the substance of the preceding level. Thus, for Aristotle, all three souls perish. For Plato however, the soul was not dependent on the physical body. Dualism is associated with the thought of René Descartes, which holds that the mind is a nonphysical—and therefore, non-spatial—substance.
Descartes identified the mind with consciousness and self-awareness and distinguished this from the brain as the seat of intelligence. Hence, he was the first to formulate the mind -- body problem in the form. Dualism is contrasted with various kinds of monism. Substance dualism is contrasted with all forms of materialism, but property dualism may be considered a form of emergent materialism or non-reductive physicalism in some sense. Ontological dualism makes dual commitments about the nature of existence as it relates to mind and matter, can be divided into three different types: Substance dualism asserts that mind and matter are fundamentally distinct kinds of foundations. Property dualism suggests that the ontological distinction lies in the differences between properties of mind and matter. Predicate dualism claims the irreducibility of mental predicates to physical predicates. Substance dualism is a type of dualism most famously defended by René Descartes, which states that there are two kinds of foundation: mental and body.
This philosophy states that the mental can exist outside of the body, the body cannot think. Substance dualism is important for having given rise to much thought regarding the famous mind–body problem. Substance dualism is a philosophical position compatible with most theologies which claim that immortal souls occupy an independent realm of existence distinct from that of the physical world. Property dualism asserts that an ontological distinction lies in the differences between properties of mind and matter, that consciousness is ontologically irreducible to neurobiology and physics, it asserts. Hence, it is a sub-branch of emergent materialism. What views properly fall under the property dualism rubric is itself a matter of dispute. There are different versions of property dualism. Non-reductive physicalism is a form of property dualism in which it is asserted that all mental states are causally reducible to physical states. One argument for this has been made in the form of anomalous monism expressed by Donald Davidson, where it is argued that mental events are identical to physical events, there can be strict law-governed causal relationships.
Another argument for this has been expressed by John Searle, the advocate of a distinctive form of physicalism he calls biological naturalism. His view is that although mental states are ontologically irreducible to physical states, they are causally reducible, he has acknowledged that "to many people" his views and those of property dualists look a lot alike. But he thinks. Epiphenomenalism is a form of property dualism, in which it is asserted that one or more mental states do not have any influence on physical states, it asserts that while material causes give rise to sensations, ideas, etc. such mental phenomena themselves cause nothing further: they are causal dead-ends. This can be contrasted to interactionism, on the other hand, in which mental causes can produce material effects, vice versa. Predicate dualism is a view espoused by nonreductive physicalists such as Donald Davidson and Jerry Fodor, who maintain that while there is only one ontological category of substances and properties of substances, the predicates that we use to describe mental events cannot be redescribed in terms of physical predicates of natural languages.
If we characterize predicate monism as the view subscribed to by eliminative materialists, who maintain that such intentional predicates as believe, think, etc. will be eliminated from both the language of science and from ordinary language because the entities to which they refer do not exist predicate dualism is most defined as the negation of this position. Predicate dualists believe that so-called "folk psychology", with all of its propositional attitude ascriptions, is an ineliminable part of the enterprise of describing and understanding human mental states and behavior. Davidson, for example, subscribes to Anomalous Monism, according to which there can be no strict psychophysical laws which connect mental and physical events under their descriptions as mental and physical events. However, all mental events have
Materialism is a form of philosophical monism which holds that matter is the fundamental substance in nature, that all things, including mental aspects and consciousness, are results of material interactions. In Idealism and consciousness are first-order realities to which matter is subject and secondary. In philosophical materialism the converse is true. Here mind and consciousness are by-products or epiphenomena of material processes without which they cannot exist. According to this doctrine the material determines consciousness, not vice versa. Materialist theories are divided into three groups. Naive materialism identifies the material world with specific elements. Metaphysical materialism examines separated parts of the world in a isolated environment. Dialectical materialism adapts the Hegelian dialectic for materialism, examining parts of the world in relation to each other within a dynamic environment. Materialism is related to physicalism, the view that all that exists is physical. Philosophical physicalism has evolved from materialism with the discoveries of the physical sciences to incorporate more sophisticated notions of physicality than mere ordinary matter, such as: spacetime, physical energies and forces, dark matter, so on.
Thus the term "physicalism" is preferred over "materialism" by some, while others use the terms as if they are synonymous. Philosophies contradictory to materialism or physicalism include idealism, pluralism and other forms of monism. Materialism belongs to the class of monist ontology; as such, it is different from ontological theories based on pluralism. For singular explanations of the phenomenal reality, materialism would be in contrast to idealism, neutral monism, spiritualism. Despite the large number of philosophical schools and subtle nuances between many, all philosophies are said to fall into one of two primary categories, which are defined in contrast to each other: idealism and materialism; the basic proposition of these two categories pertains to the nature of reality, the primary distinction between them is the way they answer two fundamental questions: "what does reality consist of?" and "how does it originate?" To idealists, spirit or mind or the objects of mind are primary, matter secondary.
To materialists, matter is primary, mind or spirit or ideas are secondary, the product of matter acting upon matter. The materialist view is best understood in its opposition to the doctrines of immaterial substance applied to the mind famously by René Descartes. However, by itself materialism says nothing about. In practice, it is assimilated to one variety of physicalism or another. Materialism is associated with reductionism, according to which the objects or phenomena individuated at one level of description, if they are genuine, must be explicable in terms of the objects or phenomena at some other level of description—typically, at a more reduced level. Non-reductive materialism explicitly rejects this notion, taking the material constitution of all particulars to be consistent with the existence of real objects, properties, or phenomena not explicable in the terms canonically used for the basic material constituents. Jerry Fodor influentially argues this view, according to which empirical laws and explanations in "special sciences" like psychology or geology are invisible from the perspective of basic physics.
A lot of vigorous literature has grown up around the relation between these views. Modern philosophical materialists extend the definition of other scientifically observable entities such as energy and the curvature of space; however philosophers such as Mary Midgley suggest that the concept of "matter" is elusive and poorly defined. Materialism contrasts with dualism, idealism and dual-aspect monism, its materiality can, in some ways, be linked to the concept of determinism, as espoused by Enlightenment thinkers. During the 19th century, Karl Marx and Friedrich Engels extended the concept of materialism to elaborate a materialist conception of history centered on the empirical world of human activity and the institutions created, reproduced, or destroyed by that activity, they developed dialectical materialism, through taking Hegelian dialectics, stripping them of their idealist aspects, fusing them with materialism. Materialism developed independently, in several geographically separated regions of Eurasia during what Karl Jaspers termed the Axial Age.
In ancient Indian philosophy, materialism developed around 600 BC with the works of Ajita Kesakambali, Payasi and the proponents of the Cārvāka school of philosophy. Kanada became one of the early proponents of atomism; the Nyaya–Vaisesika school developed one of the earliest forms of atomism, though their proofs of God and their positing that consciousness was not material precludes labelling them as materialists. Buddhist atomism and the Jaina school continued the atomic tradition. Ancient Greek atomists like Leucippus and Epicurus prefigure materialists; the Latin poem De Rerum Natura by Lucretius reflects the mechanistic philosophy of Democritus and Epicurus. According to this view, all that exists is matter and void, all phenomena result from different motions and conglomerations of base material particles called "atoms". De R
Abstraction (computer science)
In software engineering and computer science, abstraction is: the process of removing physical, spatial, or temporal details or attributes in the study of objects or systems in order to more attend to other details of interest. Abstraction, in general, is a fundamental concept to software development; the process of abstraction can be referred to as modeling and is related to the concepts of theory and design. Models can be considered types of abstractions per their generalization of aspects of reality. Abstraction in computer science is closely related to abstraction in mathematics due to their common focus on building abstractions as objects, but is related to other notions of abstraction used in other fields such as art. Abstractions may refer to vehicles, features, or rules of computational systems or programming languages that carry or utilize features of or abstraction itself, such as: the process or feature of using data types to perform data abstraction to decouple usage of from working representations of data structures within programs.
Computing operates independently of the concrete world. The hardware implements a model of computation, interchangeable with others; the software is structured in architectures to enable humans to create the enormous systems by concentrating on a few issues at a time. These architectures are made of specific choices of abstractions. Greenspun's Tenth Rule is an aphorism on how such an architecture is both complex. A central form of abstraction in computing is language abstraction: new artificial languages are developed to express specific aspects of a system. Modeling languages help in planning. Computer languages can be processed with a computer. An example of this abstraction process is the generational development of programming languages from the machine language to the assembly language and the high-level language; each stage can be used as a stepping stone for the next stage. The language abstraction continues for example in scripting languages and domain-specific programming languages. Within a programming language, some features let the programmer create new abstractions.
These include subroutines, modules and software components. Some other abstractions such as software design patterns and architectural styles remain invisible to a translator and operate only in the design of a system; some abstractions try to limit the range of concepts a programmer needs to be aware of, by hiding the abstractions that they in turn are built on. The software engineer and writer Joel Spolsky has criticised these efforts by claiming that all abstractions are leaky — that they can never hide the details below; some abstractions are designed to inter-operate with other abstractions - for example, a programming language may contain a foreign function interface for making calls to the lower-level language. In simple terms, abstraction is removing irrelevant data. Different programming languages provide different types of abstraction, depending on the intended applications for the language. For example: In object-oriented programming languages such as C++, Object Pascal, or Java, the concept of abstraction has itself become a declarative statement – using the keywords virtual or abstract and interface.
After such a declaration, it is the responsibility of the programmer to implement a class to instantiate the object of the declaration. Functional programming languages exhibit abstractions related to functions, such as lambda abstractions and higher-order functions. Modern members of the Lisp programming language family such as Clojure and Common Lisp support macro systems to allow syntactic abstraction. Other programming languages such as Scala have macros, or similar metaprogramming features; these can allow a programmer to eliminate boilerplate code, abstract away tedious function call sequences, implement new control flow structures, implement Domain Specific Languages, which allow domain-specific concepts to be expressed in concise and elegant ways. All of these, when used improve both the programmer's efficiency and the clarity of the code by making the intended purpose more explicit. A consequence of syntactic abstraction is that any Lisp dialect and in fact any programming language can, in principle, be implemented in any modern Lisp with reduced effort when compared to "more traditional" programming languages such as Python, C or Java.
Analysts have developed various methods to formally specify software systems. Some known methods include: Abstract-model based method.
Concepts are mental representations, abstract objects or abilities that make up the fundamental building blocks of thoughts and beliefs. They play an important role in all aspects of cognition. In contemporary philosophy, there are at least three prevailing ways to understand what a concept is: Concepts as mental representations, where concepts are entities that exist in the mind Concepts as abilities, where concepts are abilities peculiar to cognitive agents Concepts as Fregean senses, where concepts are abstract objects, as opposed to mental objects and mental statesConcepts can be organized into a hierarchy, higher levels of which are termed "superordinate" and lower levels termed "subordinate". Additionally, there is the "basic" or "middle" level at which people will most categorize a concept. For example, a basic-level concept would be "chair", with its superordinate, "furniture", its subordinate, "easy chair". A concept is instantiated by all of its actual or potential instances, whether these are things in the real world or other ideas.
Concepts are studied as components of human cognition in the cognitive science disciplines of linguistics and philosophy, where an ongoing debate asks whether all cognition must occur through concepts. Concepts are used as formal tools or models in mathematics, computer science and artificial intelligence where they are sometimes called classes, schema or categories. In informal use the word concept just means any idea. Within the framework of the representational theory of mind, the structural position of concepts can be understood as follows: Concepts serve as the building blocks of what are called mental representations. Mental representations, in turn, are the building blocks of, and these propositional attitudes, in turn, are the building blocks of our understanding of thoughts that populate everyday life, as well as folk psychology. In this way, we have an analysis that ties our common everyday understanding of thoughts down to the scientific and philosophical understanding of concepts.
A central question in the study of concepts is the question of. Philosophers construe this question as one about the ontology of concepts – what they are like; the ontology of concepts determines the answer to other questions, such as how to integrate concepts into a wider theory of the mind, what functions are allowed or disallowed by a concept's ontology, etc. There are two main views of the ontology of concepts: Concepts are abstract objects, concepts are mental representations. Platonist views of the mind construe concepts as abstract objects,There is debate as to the relationship between concepts and natural language. However, it is necessary at least to begin by understanding that the concept "dog" is philosophically distinct from the things in the world grouped by this concept – or the reference class or extension. Concepts that can be equated to a single word are called "lexical concepts". Study of concepts and conceptual structure falls into the disciplines of linguistics, philosophy and cognitive science.
In the simplest terms, a concept is a name or label that regards or treats an abstraction as if it had concrete or material existence, such as a person, a place, or a thing. It may represent a natural object that exists in the real world like a tree, an animal, a stone, etc, it may name an artificial object like a chair, house, etc. Abstract ideas and knowledge domains such as freedom, science, etc. are symbolized by concepts. It is important to realize that a concept is a symbol, a representation of the abstraction; the word is not to be mistaken for the thing. For example, the word "moon" is not the large, shape-changing object up in the sky, but only represents that celestial object. Concepts are created to describe and capture reality as it is known and understood. Kant maintained the view. Instead of being abstracted from individual perceptions, like empirical concepts, they originate in the mind itself, he called these concepts categories, in the sense of the word that means predicate, characteristic, or quality.
But these pure categories are predicates of things in general, not of a particular thing. According to Kant, there are twelve categories that constitute the understanding of phenomenal objects; each category is that one predicate, common to multiple empirical concepts. In order to explain how an a priori concept can relate to individual phenomena, in a manner analogous to an a posteriori concept, Kant employed the technical concept of the schema, he held that the account of the concept as an abstraction of experience is only correct. He called those concepts that result from abstraction "a posteriori concepts". An empirical or an a posteriori concept is a general representation or non-specific thought of that, common to several specific perceived objects A concept is a common feature or characteristic. Kant investigated the way; the logical acts of the understanding by which concepts are generated as to their form are: comparison, i.e. the likening of mental images to one another in relation to the unity of consciousness.