John Locke

“ What truth is. What is truth ? was an inquiry many ages since ; and it being that which all mankind either do, or pretend to search after, it cannot but be worth our while carefully to examine wherein it consists, and so acquaint ourselves with the nature of it, as to observe how the mind distinguishes it from falsehood. ”

“ But here again will be apt to occur the same doubt about truth, that did about knowledge : and it will be objected, that if truth be nothing but the joining and separating of words in propositions, as the ideas they stand for agree or disagree in men’s minds, the knowledge of truth is not so valuable a thing as it is taken to be, nor worth the pains and time men employ in the search of it : since by this account it amounts to no more than the conformity of words to the chimeras of men’s brains. ”

“ In substances, as has been already noticed, this is occasioned by the imperfections of our ideas : we making the name stand for the real essence, of which we have no idea at all. In modes, it is occasioned by the great number of simple ideas that go to the making them up. For many of them being compounded, the name occurs much easier than the complex idea itself, which requires time and attention to be recollected, and exactly represented to the mind, even in those men who have formerly been at the pains to do it ”

“ Which is a great evidence of the imperfection and uncertainty of our ideas of that kind, and may, if attentively made use of, serve for a mark to show us what are those things we have clear and perfect established ideas of, and what not. For if we will curiously observe the way our mind takes in thinking and reasoning, we shall find, I suppose, that when we make any propositions within our own thoughts about white or black, sweet or bitter, a triangle or a circle, we can and often do frame in our minds the ideas themselves, without reflecting on the names. ”

“ Some confused or obscure notions have served their turns ; and many who talk very much of religion and conscience, of church and faith, of power and right, of obstructions and humours, melancholy and choler, would perhaps have little left in their thoughts and meditations if one should desire them to think only of the things themselves and lay by those words with which they so often confound others, and not seldom themselves also. ”

“ When mental propositions contain real truth, and when verbal. Every one’s experience will satisfy him, that the mind, either by perceiving, or supposing, the agreement or disagreement of any of its ideas, does tacitly within itself put them into a kind of proposition affirmative or negative ”

“ Moral truth, which is speaking of things according to the persuasion of our own minds, though the proposition we speak agree not to the reality of things ; 2. Metaphysical truth, which is nothing but the real existence of things, conformable to the ideas to which we have annexed their names. ”

“ But this action of the mind, which is so familiar to every thinking and reasoning man, is easier to be conceived by reflecting on what passes in us when we affirm or deny, than to be explained by words. When a man has in his head the idea of two lines, viz. ”