The impression of something external on the senses, together with the state that it alone and by itself produces in us, disappears when the presence of the thing disappears. These two cannot therefore by themselves constitute genuine experience that instructs us and is supposed to guide our actions in the future. The image of the impression preserved in the imagination is already weaker than the impression itself, grows fainter every day, and disappears altogether with time.Only one thing is not subject either to the instantaneous disappearance of the impression or to the gradual disappearance of its image, and is thus free from the ravages of time: the concept. Experience of the kind that instructs us must therefore be lodged in the concept, and only the concept is fit to guide our steps securely through life. Seneca thus rightly said: ‘if you want to subordinate everything to yourself, subordinate yourself to reason’ (letter 37). And I would add that in actual life, deliberation, i.e. proceeding according to concepts, is the indispensible condition of superiority to others. An instrument of intelligence as important as concepts clearly cannot be the same as words, these mere sounds, sense impressions that fade as the present fades, or as aural illusions would fade with time. Nonetheless, the concept is a representation, and its safe keeping and clear consciousness are bound up with the word: which is why the Greeks called word, concept, relationship, thought, and reason by the name of the first of these: logos. Nevertheless, the concept is as absolutely distinct from the word it is linked to as it is from the intuitions that it arose from. It is of an entirely different nature from these sense impressions. Still, it is able to absorb all the results of intuition into itself in order to give them back, unaltered and undiminished, even after the longest stretch of time: only in this way does experience arise. But the concept does not preserve what is intuited or what is thus sensed: rather, it preserves only what is essential to this and in an entirely altered form, yet as its adequate representative.