But then, what is meant by trusting the inference of another person, and what in the other person’s narrative is free from inference? Such trust means, to be convinced that the other has made the correct analogy, has made the right use of experience, and has observed events without prejudice. That is a great deal to presuppose, and whoever takes the trouble of examining however simple and short a statement of a witness with regard to analogy, experience, and observation, must finally perceive with fear how blindly the witness has been trusted. Whoever believes in knowledge a priori will have an easy job: “The man has perceived it with his mind and reproduced it therewith; no objection may be raised to the soundness of his understanding; ergo, everything may be relied upon just as he has testified to it.” But he who believes in the more uncomfortable, but at least more conscientious, skeptical doctrine, has, at the minimum, some fair reason for believing himself able to trust the intelligence of a witness. Yet he neither is spared the task of testing the correctness of the witness’s analogy, experience and observation. Apriorism and skepticism define the great difference in the attitude toward the witness. Both skeptic and apriorist have to test the desire of the witness to lie, but only the skeptic needs to test the witness’s ability to tell the truth and his possession of sufficient understanding to reproduce correctly; to examine closely his innumerable inferences from analogy, experience and observation. That only the skeptic can be right everybody knows who has at all noticed how various people differ in regard to analogies, how very different the experiences of a single man are, both in their observation and interpretation. To distinguish these differences clearly is the main task of our investigation.