Non ridere, non lugere, neque detestari, sed intelligere. - Benedictus de Spinoza

He supported himself by grinding lenses, which was no lowly menial occupation, as it is often presented to have been in romanticizing versions of the philosopher's life, but was rather a craft that drew extensively from Spinoza's serious interest in the science of optics. The quality of his wares was highly valued by other scientists of his day. The important Dutch astronomer Christiaan Huygens, who discovered Saturn's rings as well as one of its four moons, preferred Spinoza's lenses to all others. "The [lenses] that the Jew of Voorburg has in his microscopes have an admirable polish," Huygens wrote to his brother in 1667. The one part of the romantic lens-grinding legend that is sadly true is that the dust from the optical polishing was unhealthy for Spinoza, whose mother and brother had both died young from tuberculosis. He himself succumbed to the disease at the age of forty-four.

When you say that if I deny, that the operations of seeing, hearing, attending, wishing, &c., can be ascribed to God, or that they exist in him in any eminent fashion, you do not know what sort of God mine is ; I suspect that you believe there is no greater perfection than such as can be explained by the aforesaid attributes. I am not astonished ; for I believe that, if a triangle could speak, it would say, in like manner, that God is eminently triangular, while a circle would say that the divine nature is eminently circular. Thus each would ascribe to God its own attributes, would assume itself to be like God, and look on everything else as ill-shaped. The briefness of a letter and want of time do not allow me to enter into my opinion on the divine nature, or the questions you have propounded. Besides, suggesting difficulties is not the same as producing reasons. That we do many things in the world from conjecture is true, but that our redactions are based on conjecture is false. In practical life we are compelled to follow what is most probable ; in speculative thought we are compelled to follow truth. A man would perish of hunger and thirst, if he refused to eat or drink, till he had obtained positive proof that food and drink would be good for him. But in philosophic reflection this is not so. On the contrary, we must take care not to admit as true anything, which is only probable. For when one falsity has been let in, infinite others follow. Again, we cannot infer that because sciences of things divine and human are full of controversies and quarrels, therefore their whole subject-matter is uncertain ; for there have been many persons so enamoured of contradiction, as to turn into ridicule geometrical axioms.

Hegel is (unknowingly) an admirable 'theoretician' of ideology insofar as he is a 'theoretician' of Universal Recognition who unfortunately ends up in the ideology of Absolute Knowledge. Feuerbach is an astonishing 'theoretician' of the mirror connexion, who unfortunately ends up in the ideology of the Human Essence. To find the material with which to construct a theory of the guarantee, we must turn to Spinoza.