"Again, the pen as a whole does not move in exactly the same way as its lower end; on the contrary, the upper part of the pen seems to have a quite different and opposite movement. This enables us to understand how all the movements of other animals can come about, even though we refuse to allow that they have any awareness of things, but merely grant them a purely corporeal imagination."
— Descartes, René (1596-1650)
(Rule 12, p. 41-2)
See Opuscula posthuma, physica et mathematica (Amsterdam: P. and J. Blaeu, 1701).
Not published in Descartes' lifetime. Dutch translation in 1684; published in Latin in 1701.