Full Idea
Anyone who seeks the true cause of miracles, and strives to understand natural phenomena as an intelligent being, and not to gaze at them like a fool, is denounced as an impious heretic by those whom the masses adore as interpreters of nature and gods.
Gist of Idea
Priests reject as heretics anyone who tries to understand miracles in a natural way
Source
Baruch de Spinoza (The Ethics [1675], IApp)
Book Reference
Spinoza,Benedict de: 'Ethics, Improvement of Understanding, Letters', ed/tr. Elwes,R [Dover 1955], p.78
A Reaction
A rather bitter personal remark, by someone who was driven out of Amsterdam as a heretic. Presumably the heresy is not aggressive a priori naturalism, but mere openness to the possibility of natural explanations of miracles.