My method is to call in support of my statements the evidence of a single witness, the man I am arguing with, and to take his vote alone; the rest of the world are nothing to me; I am not talking to them.

He who knows only his own side of the case knows little of that. His reasons may be good, and no one may have been able to refute them. But if he is equally unable to refute the reasons on the opposite side, if he does not so much as know what they are, he has no ground for preferring either opinion... Nor is it enough that he should hear the opinions of adversaries from his own teachers, presented as they state them, and accompanied by what they offer as refutations. He must be able to hear them from persons who actually believe them...he must know them in their most plausible and persuasive form.

I appeal to your own eyes as my witness and judge.

The truth can be perceived only through thinking, as is proven by Augustine.

Moreover, I have one request to make. I have on my own part made it my care and study that the things which I shall propound should not only be true, but should also be presented to men's minds, how strangely soever preoccupied and obstructed, in a manner not harsh or unpleasant. It is but reasonable, however (especially in so great a restoration of learning and knowledge), that I should claim of men one favor in return, which is this: if anyone would form an opinion or judgment either out of his own observation, or out of the crowd of authorities, or out of the forms of demonstration (which have now acquired a sanction like that of judicial laws), concerning these speculations of mine, let him not hope that he can do it in passage or by the by; but let him examine the thing thoroughly; let him make some little trial for himself of the way which I describe and lay out; let him familiarize his thoughts with that subtlety of nature to which experience bears witness; let him correct by seasonable patience and due delay the depraved and deep-rooted habits of his mind; and when all this is done and he has begun to be his own master, let him (if he will) use his own judgment.

The human mind may perceive truth only through thinking, as is clear from Augustine.

Defend your opinion only if it can be shown to be true, not because it is your opinion.

Many will think they may reasonably blame me by alleging that my proofs are opposed to the authority of certain men held in the highest reverence by their inexperienced judgments; not considering that my works are the issue of pure and simple experience, who is the one true mistress. These rules are sufficient to enable you to know the true from the false — and this aids men to look only for things that are possible and with due moderation — and not to wrap yourself in ignorance, a thing which can have no good result, so that in despair you would give yourself up to melancholy.

Nothing is true unless it is true in your own experience. This is your protection against being duped or misled.

My conviction is based on my own personal experiences and contacts. But having said that, I would like to assure you that what I say I present to you for your consideration only... If it appears to you to be right, logical, if it has the ring of truth... then by all means accept it, but otherwise not. I shall be perfectly content if people approach this information with an open mind. That is all I ask... I know that it is almost an impossibility.

This truth—to prove, and make thine own: ‘Thou hast been, shalt be, art, alone.’

Experiment is the sole source of truth. It alone can teach us something new; it alone can give us certainty.

All claims of education notwithstanding, the pupil will accept only that which his mind craves.

To prove cannot mean anything other than to bring the other person to my own conviction. The truth lies only in the unification of “I” and “You.” The Other of pure thought, however, is the sensuous intellect in general. In the field of philosophy, proof therefore consists only in the fact that the contradiction between sensuous intellect and pure thought is disposed, so that thought is true not only for itself but also for its opposite.