Full Idea
We do not expect that everything a rational man does should be done with a motive, ...but we do expect a man to have a motive for many things that he does, and would count anyone who constantly performed troublesome actions without a motive as irrational.
Gist of Idea
Not all actions need motives, but it is irrational to perform troublesome actions with no motive
Source
Philippa Foot (Free Will as Involving Determinism [1957], p.66)
Book Reference
Foot,Philippa: 'Virtues and Vices' [Blackwell 1981], p.66
A Reaction
Interestng, because the assessment of whether someone is 'rational' therefore needs a criterion for when a motive seems required and when not. 'Significant' actions need a motive?