The Lewis and Clark Expedition from May 1804 to September 1806 known as the Corps of Discovery Expedition, was the first American expedition to cross the western portion of the United States. It began in Pittsburgh, made its way westward, passed through the Continental Divide of the Americas to reach the Pacific coast; the Corps of Discovery was a selected group of US Army volunteers under the command of Captain Meriwether Lewis and his close friend Second Lieutenant William Clark. President Thomas Jefferson commissioned the expedition shortly after the Louisiana Purchase in 1803 to explore and to map the newly acquired territory, to find a practical route across the western half of the continent, to establish an American presence in this territory before Britain and other European powers tried to claim it; the campaign's secondary objectives were scientific and economic: to study the area's plants, animal life, geography, to establish trade with local American Indian tribes. The expedition returned to St. Louis to report its findings to Jefferson, with maps and journals in hand.

One of Thomas Jefferson's goals was to find "the most direct and practicable water communication across this continent, for the purposes of commerce." He placed special importance on declaring US sovereignty over the land occupied by the many different Indian tribes along the Missouri River, getting an accurate sense of the resources in the completed Louisiana Purchase. The expedition made notable contributions to science, but scientific research was not the main goal of the mission. During the 19th century, references to Lewis and Clark "scarcely appeared" in history books during the United States Centennial in 1876, the expedition was forgotten. Lewis and Clark began to gain attention around the start of the 20th century. Both the 1904 Louisiana Purchase Exposition in St. Louis and the 1905 Lewis and Clark Centennial Exposition in Portland, Oregon showcased them as American pioneers. However, the story remained shallow until mid-century as a celebration of US conquest and personal adventures, but more the expedition has been more researched.

In 2004, a complete and reliable set of the expedition's journals was compiled by Gary E. Moulton. In the 2000s, the bicentennial of the expedition further elevated popular interest in Lewis and Clark; as of 1984, no US exploration party was more famous, no American expedition leaders are more recognizable by name. For years, Thomas Jefferson had heard of and read accounts about the ventures of various explorers in the western frontier, had a long-held interest in further exploring this unknown region of the continent. In the 1780s, while Minister to France, Jefferson met John Ledyard in Paris in the 1780s, they discussed a possible trip to the Pacific Northwest. Jefferson had read Captain James Cook's A Voyage to the Pacific Ocean, an account of Cook's third voyage, Le Page du Pratz's The History of Louisiana, all of which influenced his decision to send an expedition. Like Captain Cook, he wished to discover a practical route through the Northwest to the Pacific coast. Alexander Mackenzie had charted a route in his quest for the Pacific, following the Mackenzie River to the Arctic Ocean in 1789.

Mackenzie and his party were the first to cross America north of Mexico to the Pacific when he arrived near Bella Coola, British Columbia in 1793–a dozen years before Lewis and Clark. Mackenzie's accounts in Voyages from Montreal informed Jefferson of Britain's intent to control the lucrative fur trade of the Columbia River and convinced him of the importance of securing the territory as soon as possible. Two years into his presidency, Jefferson asked Congress to fund an expedition through the Louisiana territory to the Pacific Ocean, he did not attempt to make a secret of the Lewis and Clark expedition from Spanish and British officials, but rather claimed different reasons for the venture. He used a secret message to ask for funding due to poor relations with the opposition Federalist Party in Congress. Congress subsequently appropriated $2,324 for supplies and food, the appropriation of, left in Lewis's charge. In 1803, Jefferson commissioned the Corps of Discovery and named Army Captain Meriwether Lewis its leader, who selected William Clark as second in command.

Lewis demonstrated remarkable skills and potential as a frontiersman, Jefferson made efforts to prepare him for the long journey ahead as the expedition was gaining approval and funding. Jefferson explained his choice of Lewis: It was impossible to find a character who to a complete science in botany, natural history, mineralogy & astronomy, joined the firmness of constitution & character, habits adapted to the woods & a familiarity with the Indian manners and character, requisite for this undertaking. All the latter qualifications Capt. Lewis has. In 1803, Jefferson sent Lewis to Philadelphia to study medicinal cures under Benjamin Rush, a physician and humanitarian, he arranged for Lewis to be further educated by Andrew Ellicott, an astronomer who instructed him in the use of the sextant and other navigational instruments. Lewis, was not ignorant of science and had demonstrated a marked capacity to learn with Jefferson as his teacher. At Monticello, Jefferson possessed an enormous library on the subject of the geography of the North American continent, Lewis had full access to it.

He spent time conferring with Jefferson. The keelboat used for the first year of the journey was built near Pittsburgh PA July 1803 at Lewis' specifications and much of the equipment and provisions were loaded into it when built. Lewis and

An ideal speech situation was a term introduced in the early philosophy of Jürgen Habermas. It argues that an ideal speech situation is found when communication between individuals is governed by basic, implied rules. In an ideal speech situation, participants would be able to evaluate each other’s assertions on the basis of reason and evidence in an atmosphere free of any nonrational “coercive” influences, including both physical and psychological coercion. Furthermore, all participants would be motivated by the desire to obtain a rational consensus. Members of the public sphere must adhere to certain rules for an "ideal speech situation" to occur, they are: 1. Every subject with the competence to speak and act is allowed to take part in a discourse. 2a. Everyone is allowed to question any assertion whatever. 2b. Everyone is allowed to introduce any assertion whatever into the discourse. 2c. Everyone is allowed to express their attitudes and needs without any hesitation. 3. No speaker may be prevented, by internal or external coercion, from exercising his rights as laid down in and The concept of the ideal speech situation came under attack in the 1970s by theorists who persistently relativized the concept, arguing that any particular conception of an ideal speech situation could not be proven correct, so that any gaps would allow associated oppressions to arise or persist.

Habermas responded to this in 1983 with Communicative Action. In this work he no longer spoke of a known ideal speech situation but instead of a new moral system that could be derived from the "presuppositions of argumentation"; these in turn could be postulated by philosophical analysis in the same way that Immanuel Kant tried to justify his own moral system through transcendental arguments. However, in contradistinction to Kant, Habermas recognizes that the presuppositions of argumentation can be tested in practice by a device he terms "performative contradiction". If critics object to the presuppositions of argumentation, their argument might be turned on them to demonstrate that their argument has granted the existence of whatever specific presupposition of argument they object to. However, if such a performative contradiction cannot be found the presuppositions of argumentation must be revised to take account of the criticism and the moral system derived from these presuppositions altered accordingly.

In other words, "performative contradiction" is not a trump card to dismiss all objections but a fair test of those objections. The dialectical nature of Habermas's argument goes unrecognized; the ideal speech situation, in its assumption of literal rather than figurative language function, is taken as the model for formal pragmatic analysis of speech-acts. The Theory of Communicative Action 1973a. Wahrheitstheorien. In H. Fahrenbach, Wirklichkeit und Reflexion. Pfüllingen: Neske. 211–265. Reprint: 1984b, chap. 2. 1971/2001. Reflections on the linguistic foundations of sociology: The Christian Gauss Lectures. * In Habermas, On the Pragmatics of Social Interaction, B. Fultner. Cambridge, MA: MIT Press, 2001. 1–103. Habermas's Discourse Theory, The Stanford Encyclopedia of Philosophy

Physoschistura is a genus of fish in the family Nemacheilidae found in Southeast Asia. There are 12 recognized species in this genus: Physoschistura brunneana Physoschistura chhimtuipuiensis Lalramliana, Solo & Vanramliana, 2016 Physoschistura chindwinensis Lokeshwor & Vishwanath, 2012 Physoschistura chulabhornae Suvarnaraksha, 2013 Physoschistura dikrongensis Lokeshwor & Vishwanath, 2012 Physoschistura elongata N. Sen & Nalbant, 1982 Physoschistura pseudobrunneana Kottelat, 1990 Physoschistura raoi Physoschistura rivulicola Physoschistura shanensis Physoschistura tigrinum Lokeshwor & Vishwanath, 2012 Physoschistura tuivaiensis Lokeshwor, Vishwanath & Shanta, 2012