It might seem strange to a man not well acquainted with the world, and in particular with the philosophical and theological tribe, that so much precaution should be necessary in the communication of our thoughts on any subject of the first philosophy, which is of common concern to the whole race of mankind, and wherein no one can have, according to nature and truth, any separate interest. Yet so it is. The separate interests we cannot have by God’s institutions, are created by those of man; and there is no subject on which men deal more unfairly with one another than this. There are separate interests, to mention them in general only, of prejudice and of profession. By the first, men set out in the search of truth under the conduct of error, and work up their heated imaginations often to such a delirium that the more genius, and the more learning they have, the madder they grow. By the second, they are sworn, as it were, to follow all their lives the authority of some particular school, to which “tanquam scopulo, adhærescunt;” for the condition of their engagement is to defend certain doctrines, and even mere forms of speech, without examination, or to examine only in order to defend them. By both, they become philosophers as men became Christians in the primitive Church, or as they determined themselves about disputed doctrines; for says Hilarius, writing to St. Austin, “Your holiness knows that the greatest part of the faithful embrace, or refuse to embrace, a doctrine for no reason but the impression which the name and authority of some body or other makes on them.” What now can a man who seeks truth for the sake of truth, and is indifferent where he finds it, expect from any communication of his thoughts to such men as these? He will be much deceived if he expects anything better than imposition or altercation. Few men have, I believe, consulted others, both the living and the dead, with less presumption, and in a greater spirit of docility, than I have done: and the more I have consulted, the less have I found of that inward conviction on which a mind that is not absolutely implicit can rest. I thought for a time that this must be my fault. I distrusted myself, not my teachers—men of the greatest name, ancient and modern. But I found at last that it was safer to trust myself than them, and to proceed by the light of my own understanding than to wander after these _ignes fatui_ of philosophy. If I am able therefore to tell you easily, and at the same time so clearly and distinctly as to be easily understood, and so strongly as not to be easily refuted, how I have thought for myself, I shall be persuaded that I have thought enough on these subjects. If I am not able to do this, it will be evident that I have not thought on them enough. I must review my opinions, discover and correct my errors.