Both Uses

motive
in
William Wilson
(Auto-generated)

That he was overcome by the wine just swallowed, was the idea which most readily presented itself; and, rather with a view to the preservation of my own character in the eyes of my associates, than from any less interested motive, I was about to insist, peremptorily, upon a discontinuance of the play, when some expressions at my elbow from among the company, and an ejaculation evincing utter despair on the part of Glendinning, gave me to understand that I had effected his total ruin under circumstances which, rendering him an object for the pity of all, should have protected him from the ill offices even of a fiend.†
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motive = reason (for doing something)
The difficulty, too, of forcing my way through the mazes of the company contributed not a little to the ruffling of my temper; for I was anxiously seeking, (let me not say with what unworthy motive) the young, the gay, the beautiful wife of the aged and doting Di Broglio.†

Definitions:

(1) (motive as in: What is her motive?)
a reason for doing something
(2) (meaning too rare to warrant focus)
Less commonly, motive can refer to something that causes motion in an inanimate object. Even less commonly, it can refer to a distinctive feature in music, art, or literature.