Baruch de Spinoza looking at a pebble at his workbench

The stone that believes itself free

Baruch de Spinoza (1632–1677) was a Dutch philosopher. In a letter written in 1674 he invites his reader to try a thought experiment. A stone receives a push and continues moving. Now imagine that for a moment it could notice its own motion.

What the stone knows about itself

The imaginary stone feels its own effort to keep going. That feeling alone tells it nothing about the push that set it moving. Seen from outside, the cause is easy to recognise. From within, continuing to fly feels exactly like something the stone wants to do.[1]

Further conceive, I beg, that a stone, while continuing in motion, should be capable of thinking and knowing, that it is endeavouring, as far as it can, to continue to move. Such a stone, being conscious merely of its own endeavour and not at all indifferent, would believe itself to be completely free, and would think that it continued in motion solely because of its own wish.[1]

What the example asks of us

Spinoza asks his correspondent to make the same distinction about human wishes. A person can certainly be aware of wanting something. Knowing how that desire arose is a separate matter. The stone brings the gap between these two kinds of knowledge into view.[1]