Full Idea
There can be no will without such a degree of understanding, at least, as gives the conception of that which we will.
Gist of Idea
A willed action needs reasonable understanding of what is to be done
Source
Thomas Reid (Essays on Active Powers 4: Liberty of Agents [1788], 1)
Book Reference
Reid,Thomas: 'Inquiry and Essays', ed/tr. Beanblossom /K.Lehrer [Hackett 1983], p.324
A Reaction
Presumably this 'conception' includes an understanding of the probable consequences, but they are of infinite complexity. I see this as an objection to 'ultimate' free will and responsibility, because there are only ever degrees of understanding.