René Descartes
René Descartes
(1596 - 1650)




Review, Part #3


Scientists, rationalists, such as Rene Descartes (1596-1650) and Galileo explained the nature and activity of bodies by concentrating on their measurable aspects. Universal laws were stated in quantitative terms, and the behavior of individual bodies or classes of bodies was shown to follow logically from these laws. Benedictus (also Baruch) Spinoza (1632-1677), like Descartes, saw this as just one application of a method that could be applied to everything that human beings are capable of knowing. Spinoza's main interests lay in the field of moral philosophy, and in his Ethics (Ethica Ordine Geometrico Demonstrata) he presented his views about the nature of the good in the form of the Euclid's (fl. c.300 BC) geometry, the most perfect deductive system known to him. Gottfried Wilhelm Leibniz (1646-1716) agreed with Spinoza that everything is explicable. "There cannot", he wrote, "be any true of existent fact, or any true proposition, without there being a sufficient reason why it should be so and not otherwise" (Monadology, par. 32), and he called this the principle of a sufficient reason. Leibniz asserts (in his basic ontological thesis) that the basic individuals of an acceptable ontology are all monads, i.e., immaterial entities lacking spatial parts, whose basic properties are a function of their perceptions and appetites. He differed from Spinoza, however, in that he denied that all explanation is deduction from logically necessary truths. The laws of nature are indeed necessary; it does not, for example, just happen that light travels in straight lines. But they are not logically necessary, they are hypothetically necessary. In 1900 Bertrand Russell published an important study, A Critical Exposition of the Philosophy of Leibniz, in which he drew attention to the part played in that philosophy by logic. Russell took logic in a broad sense, so as to include theories about the structure of the proposition and the nature of truth. This approach to Leibniz is still a helpful one.

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The English philosopher John Locke (1632-1704) did at the end of 17th century a corresponding difference between primary qualities in objects and secondary qualities in the mind of the conscious subject. George Berkeley (1685-1753) claimed against Locke in 18th century, that all qualities are subjective and that qualities can not be separated from the others. E.g. every person, which we can imagine, have also a color - so according to Berkeley an idea of fully abstract person exist not even in the mind of human being. Berkeley's view to the problem of general concepts is thus nominalistic.

David Hume (1711-1776) separated on 18th century, from the others, truths which are expressing relations between ideas of human mind (like "three times five is half of thirty"), and truths which are related to facts (like "sun rises tomorrow"). These kind of truths may be called abstract truths and factual truths. Latter truths are material truths, which are dealing with reality or facts, whereas previous truths are independent of the prevailing conditions. Abstract truths haven't any content of facts - at most they are expressing something about which concept-system is in use while describing the reality.

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