To appreciate the influence, covert or overt, of scepticism in the Middle Ages we must clear the meaning of the word. Under the yoke of tribal custom scepticism can hardly arise, there is no place for the half-hearted, as all men feel alike so all think alike: scepticism arises when beliefs are put into formal propositions. Then, as experience and comparison enlarge, we detect scepticism in three forms or degrees: namely, doubt of a particular creed; doubt of all unverified propositions; and doubt of the validity of reason itself, whether in respect of the supernatural only or of all argument. It is remarkable that this last, the most devastating of the forms of scepticism, has come from the ranks of the faithful (Pascal, Hamilton, Mansel), who in resentment of the attacks of reason have turned blindly to rend reason herself. No civil society has been without scepticism; even in ages of most prevalent faith some current of doubt has flowed under the surface. In the Ionian philosophy the place of scepticism was only restricted in so far as many aspects of the subject-matter were not before those thinkers; for instance no Greek philosopher would have separated faith from reason. In the well-known words of Hippocrates, “οὐδὲν ἕτερον ἑτέρου θειότερον οὐδὲ ἀνθρωπινώτερον, ἀλλὰ πάντα θεῖα.” “The Greek boldly set up his academy by the side of the temple.” Even Protagoras never taught the futility of all reason, nor even the inconstancy of sensation which indeed is doctrine rather than scepticism. Neo-platonism had its scepticism in the first two forms, covering even the ground of the modern agnostic. Agnosticism does not deny the existence of the ladder, but asserts that the ladder begins and ends in the clouds; it is consistent therefore with ethical and practical activity. When Abélard said “Dubitando enim ad inquisitionem venimus, inquirendo veritatem percipimus,” if a sceptic, he was no infidel. Even in the thirteenth century it was never doubted that truth is attainable, nor indeed that the Faith contained the truth. The scepticism of that age was rather cautious and controversial than faithless, and in practice divine discontent rather than indifference (ἀταραξία). Pyrrhonism on the other hand leads to slackness of ethics; either to the insouciance of Horace and Montaigne, or to the attitude of the seventeenth century in Padua (Pomponatius) and elsewhere, when the “economy,” ironic or disingenuous, of allotting their several spheres to reason and dogma, if not first invented, became as fashionable as in the pulpits and in the drawing-rooms of Mayfair. “Comme savant j’ignore tout; comme citoyen je crois tout.” The _Hypotyposes Pyrrhoniœ_ of Sextus Empiricus, whose influence in the times of the Renascence was considerable, was not translated till the fourteenth century. The detachment of mind and shrewd wisdom of John of Salisbury foreshadowed Petrarch rather than Hume; and when John discusses what it is given to man to know, asking