As is well known, a great flowering of Neo-Spinozism occurred in German philosophy and literature in the late eighteenth and early nineteenth centuri… - Benedictus de Spinoza

[T]hese instances are enough to show, that the body can by the sole laws of its nature do many things which the mind wonders at.

For Spinoza, by contrast, there is to be no criminalization of ideas in the well-ordered state. Libertas philosophandi, the freedom of philosophizing, must be upheld for the sake of a healthy, secure and peaceful commonwealth and material and intellectual progress.

...Note that in saying this, Feuerbach stands close to Spinoza, whose philosophy he was already setting forth with great sympathy at the time his own breakaway from idealism was taking shape, that is, when he was writing his history of modern philosophy. In 1843 he made the subtle observation, in his Grundsätze, that pantheism is a theological materialism, a negation of theology but as yet on a theological standpoint. This confusion of materialism and theology constituted Spinoza's inconsistency, which, however, did not prevent him from providing a ‘correct – at least for his time – philosophical expression for the materialist trend of modern times’. That was why Feuerbach called Spinoza ‘the Moses of the modern free-thinkers and materialists’. In 1847 Feuerbach asked: ‘What then, under careful examination, is that which Spinoza calls Substance, in terms of logics or metaphysics, and God in terms of theology?’ To this question he replied categorically: ‘Nothing else but Nature.’ He saw Spinozism’s main shortcoming in the fact that ‘in it the sensible, anti-theological essence of Nature assumes the aspect of an abstract, metaphysical being’. Spinoza eliminated the dualism of God and Nature, since he declared that the acts of Nature were those of God. However, it was just because he regarded the acts of Nature to be those of God, that the latter remained, with Spinoza, a being distinct from Nature, but forming its foundation. He regarded God as the subject and Nature as the predicate. A philosophy that has completely liberated itself from theological traditions must remove this important shortcoming in Spinoza's philosophy, which in its essence is sound. ‘Away with this contradiction!’, Feuerbach exclaimed. ‘Not Deus sive Natura but aut Deus aut Natura is the watchword of Truth.’ Thus, Feuerbach's ‘humanism’ proved to be nothing else but Spinozism disencumbered of its theological pendant. And it was the standpoint of this kind of Spinozism, which Feuerbach had freed of its theological pendant, that Marx and Engels adopted when they broke with idealism. However, disencumbering Spinozism of its theological appendage meant revealing its true and materialist content. Consequently, the Spinozism of Marx and Engels was indeed materialism brought up to date.