David Hume, A Treatise of Human Nature, vol. 2 (1793), p. 218

Throw in a superior degree of probability to the side of grief, you immediately see that the passion diffuses itself over the composition, and tinctures it into fear. Encrease the probability and by that means the grief, the fear prevails still more and more, till at last it runs insensibly, as the joy continually diminishes, into pure grief.

Here, Hume describes the movements of the passions as if they were colors of the prism bleeding into one another. Emotion is described as a continual flow from one state to another. Fear and grief become a complex "tincture" of imagination, natural emotion and physical response. Once the process is underway, once one begins the move towards "pure grief," one can see where it would be difficult to turn back, just as colors can be pried out of white light only under entirely artificial circumstances.

Related terms:

a dictionary of sensibility
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