In the strident world of seventeenth-century philosophy, the mind-body problem was not a word puzzle that could be safely relegated to undergraduate … - Benedictus de Spinoza

Nothing in Nature is random. A thing appears random only through the incompleteness of our knowledge.

From Descartes and Malebranche onward, the metaphysical value of the “idea” or archetype steadily deteriorated. It became a “thought,” an internal condition of cognition, as clearly formulated by Spinoza: “By 'idea' I understand a conception of the mind which the mind forms by reason of its being a thinking thing.” Finally Kant reduced the archetypes to a limited number of categories of understanding.

Hence it inevitably follows logically, as Engels said, ‘that matter remains eternally the same in all its transformations, that none of its attributes can ever be lost, and therefore, also, that with the same iron necessity that it will exterminate on the earth its highest creation, the thinking mind, it must somewhere else and at another time again produce it.’ That was Spinoza's standpoint, a circumstance that seemingly gave Engels grounds for replying categorically and unambiguously to Plekhanov when he asked: ‘So in your opinion old Spinoza was right in saying that thought and extension were nothing but two attributes of one and the same substance?’ "Of course," answered Engels, "old Spinoza was quite right".’ Spinoza's definition means the following: in man, as in any other possible thinking creature, the same matter thinks as in other cases (other modi) only ‘extends’ in the form of stones or any other ‘unthinking body’; that thought in fact cannot be separated from world matter and counterposed to it itself as a special, incorporeal ‘soul’, and it (thought) is matter’s own perfection. That is how Herder and Goethe, La Mettrie and Diderot, Marx and Plekhanov (all great ‘Spinozists’) and even the young Schelling, understood Spinoza. [...] Spinoza said more than once that it was impermissible to represent thought as attribute in the image and likeness of human thought; it was only the universal property of substance that was the basis of any ‘finite thought’, including human thought, but in no case was it identical with it. To represent thought in general in the image and likeness of existing human thought, of its modus, or ‘particular case’, meant simply to represent it incorrectly, in ‘an incomplete way’, by a ‘model’, so to say, of its far from most perfected image (although the most perfected known to us).