In 1780 Jacobi had his historic conversation with Lessing at Wolfenbüttel[7]. The talk turned on Spinoza. For many years the philosophy of Spinoza had seemed to vanish from the world. His name was only heard in a reference of obloquy, as if it were dangerous to be even suspected of infection with the taint of Atheism. But both Lessing and Jacobi had found him out. The former saw in him an ally in that struggle for higher light and wider views which he undertook in a spirit and with a scope hardly surmised by those he usually wrought with. Jacobi, on the contrary, saw in him personified the conjunction of all those irreligious tendencies which all philosophy in some degree exhibited: the tendency to veil or set aside God and personality. 'I believe,' says Jacobi, as he began the conversation 'in an intelligent personal cause of the world.' 'Then I am going,' replied Lessing, 'to hear something quite new': and he dryly put aside the other's rhapsody on the 'personal extra-mundane deity with the remark 'Words, my dear Jacobi, words.' Jacobi's work _Letters on the doctrine of Spinoza_ (it appeared in 1785) was the beginning of a controversy in which Mendelssohn and Herder took part, and in which Goethe took an interest under Herders tutorship. To the exact philological study of Spinoza it did not contribute much: for the Spinoza whom Herder and Goethe saw as their spiritual forefather was transfigured in their thought to a figure to which Leibniz had almost an equal right to give his name. He upheld to them the symbol of the immanence of the divine in nature: he was the leader in the battle against 'philistine' deism and utilitarianism.
With the Kantian criticism of the pseudo-science of theology Jacobi had in one way no fault to find. That reasoning by its demonstration cannot find out God, was to him an axiomatic belief. But the 'man of feeling' felt uneasy at the trenchant methods of the Königsberg man of logic. He seemed to see the world of men and things passing under Kant's manipulation into a mere collection of phenomena and ideas of the mind. Still more was he sensible to the loss of his God. That surrogate of an argument for theism which Kant seemed to offer in the implications of the Moral Law did not give what Jacobi wanted. Mere morality is a cold and mechanical principle--he thinks--compared with that infinite life and love which we deem we have in God. The son of man, he felt, was, in virtue of an indwelling genius of conscience, supreme over the moral law: how much more, then, the Absolute and Eternal on a higher grade of being than its mechanical regularities!