Yet, in spite of Plato and his followers, mankind have again and again returned to a sensational philosophy. As to some of the early thinkers, amid the fleetings of sensible objects, ideas alone seemed to be fixed, so to a later generation amid the fluctuation of philosophical opinions the only fixed points appeared to be outward objects. Any pretence of knowledge which went beyond them implied logical processes, of the correctness of which they had no assurance and which at best were only probable. The mind, tired of wandering, sought to rest on firm ground; when the idols of philosophy and language were stripped off, the perception of outward objects alone remained. The ancient Epicureans never asked whether the comparison of these with one another did not involve principles of another kind which were above and beyond them. In like manner the modern inductive philosophy forgot to enquire into the meaning of experience, and did not attempt to form a conception of outward objects apart from the mind, or of the mind apart from them. Soon objects of sense were merged in sensations and feelings, but feelings and sensations were still unanalyzed. At last we return to the doctrine attributed by Plato to Protagoras, that the mind is only a succession of momentary perceptions. At this point the modern philosophy of experience forms an alliance with ancient scepticism. The higher truths of philosophy and religion are very far removed from sense. Admitting that, like all other knowledge, they are derived from experience, and that experience is ultimately resolvable into facts which come to us through the eye and ear, still their origin is a mere accident which has nothing to do with their true nature. They are universal and unseen; they belong to all times--past, present, and future. Any worthy notion of mind or reason includes them. The proof of them is, 1st, their comprehensiveness and consistency with one another; 2ndly, their agreement with history and experience. But sensation is of the present only, is isolated, is and is not in successive moments. It takes the passing hour as it comes, following the lead of the eye or ear instead of the command of reason. It is a faculty which man has in common with the animals, and in which he is inferior to many of them. The importance of the senses in us is that they are the apertures of the mind, doors and windows through which we take in and make our own the materials of knowledge. Regarded in any other point of view sensation is of all mental acts the most trivial and superficial. Hence the term 'sensational' is rightly used to express what is shallow in thought and feeling. We propose in what follows, first of all, like Plato in the Theaetetus, to analyse sensation, and secondly to trace the connexion between theories of sensation and a sensational or Epicurean philosophy.