Those of direct and easy revivability (visual, auditory, tactile-motor, with some reservations for the last named). Those of indirect and comparatively easy revivability: pleasures and pains, emotions. They are indirect, because the emotional state is only induced through the intermediary of the intellectual states with which it is associated.[104] ----- Footnote 104: A characteristic peculiar to emotional affective revivability is the slowness with which it develops and the time required. While the visual or auditory image may be called up instantaneously and at command, the emotional representation arises slowly. This is because it passes through two stages. The first (intellectual) consists in the evocation of conditions and circumstances—a toothache, a burn, a passion. Many do not get beyond this stage, and the concomitant emotional tone, accordingly, is faint, or even _nil_. The second or emotional stage adds to this the rise of states of excitement and exultation, or of dejection and lowered vitality. The latter requires organic conditions, a difference in the organism, an excitement of the motor, vascular, respiratory, secretory, and other centres. ----- Those of difficult revivability, either direct or indirect. This heterogeneous and difficult group includes tastes, odours, and internal sensations. What are the reasons for these differences? I reduce them to two principal ones, which I may briefly state thus— The revivability of an impression is in direct ratio to its complexity, and consequently in inverse ratio to its simplicity. The revivability of an impression (with certain exceptions to be mentioned afterwards) is in direct ratio to the motor elements included in it. 1. It is an incontestable fact that an isolated state of consciousness, with no relation to what precedes, accompanies, or follows it, has small chance of fixing itself in the memory. I hear a word of an unknown language, it immediately vanishes; but if I read and write it, if I associate it with some object or with various circumstances, it is fixed. It is easier to remember a group or a series than an isolated and unrelated term. Now, by their very nature, the visual images arrange themselves in complex aggregates, and the auditive in sequences (or even, in the case of harmony, in simultaneities), while the motor images are associated in series, every term of which awakens and brings with it the last. They accordingly fulfil the conditions of immediate and easy revivability. It is the same with pleasures, pains, emotions. Always connected with intellectual states (perceptions, representations, or ideas), they form part of an aggregate, and are involved in its resurgent movement. The case is different with the images of our third group. They are not associated with one another; they have an isolated and individual character; they contract no relations, either of space or time, among themselves.