imagery, are other curious circumstances of our sleeping imaginations. The
variety of scenery seems to arise from the superior activity and excellence
of our sense of vision; which in an instant unfolds to the mind extensive
fields of pleasurable ideas; while the other senses collect their objects
slowly, and with little combination; add to this, that the ideas, which
this organ presents us with, are more frequently connected with our
sensation than those of any other.

9. The great novelty of combination is owing to another circumstance; the
trains of ideas, which are carried on in our waking thoughts, are in our
dreams dissevered in a thousand places by the suspension of volition, and
the absence of irritative ideas, and are hence perpetually falling into new
catenations. As explained in Sect. XVII. 1. 9. For the power of volition is
perpetually exerted during our waking hours in comparing our passing trains
of ideas with our acquired knowledge of nature, and thus forms many
intermediate links in their catenation. And the irritative ideas excited by
the stimulus of the objects, with which we are surrounded, are every moment
intruded upon us, and form other links of our unceasing catenations of
ideas.

10. The absence of the stimuli of external bodies, and of volition, in our
dreams renders the organs of sense liable to be more strongly affected by
the powers of sensation, and of association. For our desires or aversions,
or the obtrusions of surrounding bodies, dissever the sensitive and
associate tribes of ideas in our waking hours by introducing those of
irritation and volition amongst them. Hence proceeds the superior
distinctness of pleasurable or painful imagery in our sleep; for we recal
the figure and the features of a long lost friend, whom we loved, in our
dreams with much more accuracy and vivacity than in our waking thoughts.
This circumstance contributes to prove, that our ideas of imagination are