pleasure or pain; as the ideas, which constitute our dreams or reveries,
this is called imagination.

3. Voluntary ideas are those, which are preceded by voluntary exertion, as
when I repeat the alphabet backwards: this is called recollection.

4. Associate ideas are those, which are preceded by other ideas or muscular
motions, as when we think over or repeat the alphabet by rote in its usual
order; or sing a tune we are accustomed to; this is called suggestion.

III. 1. Perceptions signify those ideas, which are preceded by irritation
and succeeded by the sensation of pleasure or pain, for whatever excites
our attention interests us; that is, it is accompanied with, pleasure or
pain; however slight may be the degree or quantity of either of them.

The word memory includes two classes of ideas, either those which, are
preceded by voluntary exertion, or those which are suggested by their
associations with other ideas.

2. Reasoning is that operation of the sensorium, by which we excite two or
many tribes of ideas; and then re-excite the ideas, in which they differ,
or correspond. If we determine this difference, it is called judgment; if
we in vain endeavour to determine it, it is called doubting.

If we re-excited the ideas, in which they differ, it is called
distinguishing. If we re-excite those in which they correspond, it is
called comparing.

3. Invention is an operation of the sensorium, by which we voluntarily
continue to excite one train of ideas, suppose the design of raising water