The wide diffusion and constant prevalence of such infirmities is attested not less by Sokrates in his last speech, wherein he declares real want of knowledge and false persuasion of knowledge, to be universal, the mission of his life being to expose them, though he could not correct them--than by Bacon in his reformatory projects, where he enumerates the various Idola worshipped by the human intellect, and the false tendencies acquired "_in primâ digestione mentis_". The psychological analysis of the sentiment of belief with its different sources, given in Mr. Alexander Bain's work on the Emotions and the Will, shows how this takes place; and exhibits true or sound belief, in so far as it ever is acquired, as an acquisition only attained after expulsion of earlier antecedent error.[61] Of such error, and of the different ways in which apparent evidence is mistaken for real evidence, a comprehensive philosophical exposition is farther given by Mr. John Stuart Mill, in the fifth book of his System of Logic, devoted to the subject of Fallacies. Every variety of erroneous procedure is referable to some one or more of the general heads of Fallacy there enumerated. It is the Fallacies of Ratiocination, of which the two Sophists, in the Platonic Euthydêmus, are made to exhibit specimens: and when we regard such Fallacies, as one branch among several in a complete logical scheme, we shall see at once that they are not inventions of the Athenian Sophists--still less inventions for the purpose of Eristic or formal debate. For every one of these Fallacies is of a nature to ensnare men, and even to ensnare them more easily, in the common, informal, conversation of life--or in their separate thoughts. Besides mistakes on matters of fact, the two main causes which promote the success and encourage the multiplication of Fallacies generally, are first, the emotional bias towards particular conclusions, which disposes persons to accept any apparent evidence, favourable to such conclusion, as if it, were real evidence: next, the careless and elliptical character of common speech, in which some parts of the evidence are merely insinuated, and other parts altogether left out. It is this last circumstance which gives occasion to the very extensive class of Fallacies called by Mr. Mill Fallacies of Confusion: a class so large, that the greater number of Fallacies might plausibly be brought under it.[62]