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 any but the highest animals. In the nature of the case satisfactory conclusions as to the rationality which may be predicated of animals are impossible.

The term “reason” is also used in several narrower senses. Thus reason is opposed to sensation, perception, feeling, desire, as the faculty (the existence of which is denied by empiricists) by which fundamental truths are intuitively apprehended. These fundamental truths are the causes or “reasons” ( ) of all derivative facts. With Kant, reason (Vernunft) is the power of synthesizing into unity, by means of comprehensive principles, the concepts provided by the intellect (Verstand). The reason which gives a priori principles Kant calls “Pure Reason” (cf. the Kritik der reinen Vernunft), as distinguished from the “Practical Reason” (praktische Vernunft) which is specially concerned with the performance of particular actions. In formal logic the drawing of inferences (frequently called “ratiocination,” from Lat. ratiocinari, to use the reasoning faculty) is classified from Aristotle downwards as deductive (from generals to particulars) and inductive (from particulars to generals); see, ,. In theology, reason, as distinguished from faith, is the human intelligence exercised upon religious truth whether by way of discovery or by way of explanation. The limits within which the reason may be used have been laid down differently in different churches and periods of thought: on the whole, modern Christianity, especially in the Protestant churches, tends to allow to reason a wide field, reserving, however, as the sphere of faith the ultimate (supernatural) truths of theology.

The Greek words for reason are  and , both vaguely used. In Aristotle the  of a thing is its definition, including its formal cause, while the ultimate principles of a science are , the “reasons” (in a common modern sense) which explain all its particular facts.  in Plato and Aristotle is used both widely for all the meanings which “reason” can have, and strictly for the faculty which apprehends intuitively. Thus, in the Republic,  is the faculty which apprehends necessary truth, while  (opinion) is concerned with phenomena.

For the Stoic and Neoplatonic uses of , as also for those of Philo Judaeus and the Fathers, see.

RÉAUMUR, RENÉ ANTOINE FERCHAULT DE (1683–1757), French man of science, was born on the 28th of February 1683 at La Rochelle and received his early education there. He was taught philosophy in the Jesuits' college at Poitiers, and in 1699 went to Bourges to study civil law and mathematics under the charge of an uncle, canon of La Sainte-Chapelle. In 1703 he came to Paris, where he continued the study of mathematics and physics, and in 1708, at the early age of twenty-four, was elected a member of the Académie des Sciences. From this time onwards for nearly half a century hardly a year passed in which the Mémoires de l’Académie did not contain at least one paper by Réaumur. At first his attention was occupied by mathematical studies, especially in geometry. In 1710 he was appointed to the charge of a great government work—the official description of the useful arts and manufactures—which led him to many practical researches that resulted in the establishment of manufactures new to France and the revival of neglected industries. For discoveries regarding iron and steel he was awarded a pension of 12,000 livres; but, being content with his ample private income, he requested that the money should be secured to the Académie des Sciences for the furtherance of experiments on improved industrial processes. In 1731 he became interested in meteorology, and invented the thermometer scale which bears his name. In 1735 family arrangements obliged him to accept the post of commander and intendant of the royal and military order of Saint-Louis; he discharged his duties with scrupulous attention, but declined the emoluments. He took great delight in the systematic study of natural history. His friends often called him the

Pliny of the 18th century. He loved retirement and lived much at his country residences, at one of which, La Bermondière (Maine), he met with a fall from horseback, the effects of which proved fatal on the 17th of October 1757. He bequeathed his manuscripts, which filled 138 portfolios, and his natural history collections to the Académie des Sciences.

Réaumur’s scientific papers deal with nearly all branches of science; his first, in 1708, was on a general problem in geometry; his last, in 1756, on the forms of birds' nests. He proved experimentally the fact that the strength of a rope is less than the sum of the strengths of its separate strands. He examined and reported on the auriferous rivers, the turquoise mines, the forests and the fossil beds of France. He devised the method of tinning iron that is still employed, and investigated the differences between iron and steel, correctly showing that the amount of carbon (sulphur in the language of the old chemistry) is greatest in cast iron, less in steel, and least in wrought iron. His book on this subject (1722) was translated into English and German. The thermometer by which he is now best remembered was constructed on the principle of taking the freezing-point of water as 0°, and graduating the tube into degrees each of which was one-thousandth of the volume contained by the bulb and tube up to the zero mark. It was an accident dependent on the dilatability of the particular quality of alcohol employed which made the boiling point of water 80°; and mercurial thermometers the stems of which are graduated into eighty equal parts between the freezing- and boiling-points of water are not Réaumur thermometers in anything but name.

REBAB, or (Persian rubāb; Arabic rabāb, rabāba; Sp. ravé, rabé, rabel, arrabel, arrabil; Fr. rubèbe; It. rubeba), an ancient stringed instrument, having a body either pear-shaped or boat-shaped and the characteristics of vaulted back and the absence of neck; also a generic modern Arabic term applied by the Mahommedans of northern Africa to various stringed instruments played with a bow.

As the rebab exercised a very considerable influence on the history of stringed instruments in Europe, and was undoubtedly the means through which the bow was introduced to the West, it is necessary to examine its construction before deciding whether it may be accepted as the ancestor of the violin in deference to the claim made for it by certain modern writers.