R. G. Collingwood, The Idea of History, 83:

Hume's abolition of spiritual substance
amounted to laying down the principle that
we must never separate what a mind is from what it does,
and that therefore a mind's nature is nothing but
the ways in which it thinks and acts.

The concept of mental substance
was thus resolved into the concept of mental process.
But this did not in itself necessitate
an historical conception of mind,
because all process is not historical process.
A process is historical only when it creates its own laws,
and according to Hume's theory of mind the laws of
mental process are ready-made and unchanging from their beginning.