For a long time, the thesis of the eternity of the intellect – a thesis that crowns Part V of the Ethics – was subject to controversies, reviving the perennial quarrel concerning Spinoza's atheism. It disturbed believers as much as unbelievers, who strived either to drive the unholy man out from under the protective cloak of honest people's faith, or else to ultimately lead the mystic back to the flock of the religious tradition. Lerminier, a professor of law at the Collège de France, echoes this suspicion in his Philosophie du droit, published in 1831. Concerning Spinoza's record, he feels that

Lerminier concludes his diatribe by denouncing the impotence of a pantheism that ‘can only deliver to man one of two things: a series of terrestrial existences and transformations or an irrevocable void (néant)’.

For diametrically opposed reasons, certain Marxist thinkers also wonder what to make of this ‘something that remains and vexes us with its eternity’. Helmut Seidel, for example, after having recognised in Spinoza a precursor of dialectical materialism, finds the introduction of a metaphysical conception sub specie aeternitatis regrettable and critiques this as a hangover of ancient origin. This discomfort and its proceeding incomprehension sometimes take the form of pure and simple obfuscation. In this way, Marianne Schaub, in her general presentation of Spinoza, does not mention the presence of this theory of the intellect's eternity and makes absolutely no reference to it. Does such an omission constitute a cautious effort to steer clear of a rather thorny issue, or, instead, an underestimation of the importance of the mind's eternity?