人类理解研究

Chapter 4: Some doubts about the role of understanding Section 1 All objects of human reason (or research) can be naturally divided into two kinds, namely, relations of ideas (Relations of Ideas) and actual things (Matters of  F act). Of the first kind are the sciences of geometry, algebra, and trigonometry; in a word, any assertion which has the certainty of intuition or the certainty of solution belongs to the former kind. Propositions of this kind we can find out by the action of thought alone, and need not be based on anything existing anywhere in the universe. Even if there is not a circle or a triangle in nature, the truths that Euclid has solved will always remain true and intelligible. As for the second object of human reason - actual things - they cannot be examined in the same way; and no matter how clear we are about their truth, that clarity is not the same as the previous one. The opposite of every kind of fact is always possible; for it never contains any contradiction, and the mind conceives it lightly and clearly, just as the opposite of that fact fits well into the real situation. All theories of practical matters seem to be based on the relation of cause and effect. By virtue of this relationship alone, we can go beyond the evidence of our memory and senses. I can boldly make the general proposition, without exception, that the knowledge of this relation does not, in any instance, arise from a priori inference; it arises solely because we see, from experience, that certain particular objects are constantly connected with each other. No matter how strong one's natural reason and talent may be, he cannot discover any kind of cause or effect of an entirely new object when he encounters it, even if he has examined its sensible properties with great precision. We can say that "cause and effect are discovered not by reason, but by experience". In short, every result is a different thing from its cause. Therefore, it cannot be found in its cause; therefore, the result that one starts with a priori, that one creates, that one imagines, must be completely arbitrary. Even after this result is suggested, its connection with the cause is just as arbitrary, for there are always many other results that appear to reason to be just as fully self-consistent and natural. Therefore, apart from the help of observation and experience, we cannot presume to decide anything, or to infer any cause or effect. When an object or cause is presented to our mind, it can never suggest the idea of any other object-such as a result, much less the indissoluble and unbreakable connection between cause and effect-if we do not infer it and examine it a priori by means of some observation.