Full Idea
When men make mistakes in calculation, they have one set of figures in their mind, and another on the paper. If we could see into their minds, they do not make a mistake.
Gist of Idea
People make calculation mistakes by misjudging the figures, not calculating them wrongly
Source
Baruch de Spinoza (The Ethics [1675], II Pr 47)
Book Reference
Spinoza,Benedict de: 'Ethics, Improvement of Understanding, Letters', ed/tr. Elwes,R [Dover 1955], p.119
A Reaction
A wonderfully optimistic assertion of faith in reason! He seems to imply an infallibility in reason, which seems a bit implausible. If I make 7+6=14, MUST I have muddled the 6 with a 7? Presumably Spinoza was good at arithmetic.
Related Idea
Idea 4764 We cannot directly control our beliefs, but we can control the causes of our involuntary beliefs [Engel]