the result which he presented was logical, it only led to a higher truth.  It was reserved for the greatest of modern philosophers to reveal to the world that causality is a condition, and a necessary condition, of thought.  When Aenesidemus proved by his seventh Trope that causality is subjective, he regarded it as fatal to the doctrine; yet this conclusion was a marked step in advance in critical philosophy, although Aenesidemus could not himself see it in all its bearings.  The great difference between Aenesidemus and Kant is the difference between the materialist and the believer in subjective reality.  Both agreed in the unknown nature of the Ding an sich, but this was to the Pyrrhonist the end of all his philosophy; to Kant, however, the beginning.

Pyrrhonism has rendered, notwithstanding its points of fatal weakness, marked service to the world in science, philosophy, ethics, and religion.  It quickened scientific thought by emphasising empirical methods of investigation, and by criticising all results founded without sufficient data upon false hypotheses.  If, instead of denying the possibility of all science because of the want of a criterion of the truth of phenomena, the Pyrrhonists had comprehended the possibility of a science of phenomena, they might have led the world in scientific progress.[1] Their service to philosophy lay in the stimulus to thought that their frequent attacks on dogmatic beliefs occasioned.  Pyrrhonism brought together all the most prominent theories of the old schools of philosophy to test their weakness and expose their contradictions, and this very process of criticism often demonstrated the power of the truth which they contained.

Sextus Empiricus was often charged by the Church Fathers with corrupting religious belief, and yet the greatest service which Pyrrhonism has rendered the world was in religious and ethical lines.  This service did not, naturally, consist in destroying belief in absolute truth, as the Sceptic professed to do, but in preparing the way to find it.  The bold attacks of Scepticism on all truth led men to investigate ethical and religious teachings, to examine the grounds of their belief, and to put in practical use the right of reason and free discussion.

Scepticism was the antecedent of freedom of conscience and rational criticism,[2] and the absolute right of scientific thought.  The Sceptics, however, reaped none of the benefits of their own system.  They remained, as it were, always on the threshold of possible progress.  With the keys to great discoveries in their hands, the doors of philosophical and scientific advancement were for ever closed to them by the limitations of their own system.  The inherent weakness of Pyrrhonism lay in its psychological inconsistency and in its negative character.  I think that we may safely say that Pyrrhonism was the most consistent system of Scepticism ever offered to the world, and yet it proves most decidedly that complete Scepticism is psychologically impossible.  A man may give up his belief in one set of ideas, and, if they are ideas that are popularly accepted, he will be called a Sceptic, as was the case with Hume.  He must, however, replace these ideas by others equally positive, and then he is no longer a Sceptic, but a Dogmatic, for he believes in something.