We have no space to follow the reasoning by which Diderot supports this scornful estimate of the famous thinker, of whom it can never be settled whether he be pantheist, atheist, akosmist, or God-intoxicated man.  He returns to the charge again and again, as if he felt a certain secret uneasiness lest for scorn so loudly expressed he had not brought forward adequate justification.  And the reader feels that Diderot has scarcely hit the true line of cleavage that would have enabled him—­from his own point of view—­to shatter the Spinosist system.  He tries various bouts of logic with Spinosa in connection with detached propositions.  Thus he deals with Spinosa’s third proposition, that, in the case of things that have nothing in common with one another, one cannot be the cause of the other.  This proposition, Diderot contends, is false in all moral and occasional causes.  The sound of the name of God has nothing in common with the idea of the Creator which that name produces in my mind.  A misfortune that overtakes my friend has nothing in common with the grief that I feel in consequence.  When I move my arm by an act of will, the movement has nothing in common in its nature with the act of my will; they are very different.  I am not a triangle, yet I form the idea of one and I examine its properties.  So with the fifth proposition, that there cannot be in the universe two or more substances of the same nature or the same attributes.  If Spinosa is only talking of the essence of things or of their definition, what he says is naught; for it can only mean that there cannot be in the universe two different essences having the same essence.  Who doubts it?  But if Spinosa means that there cannot be an essence which is found in various single objects, in the same way as the essence of triangle is found in the triangle A and the triangle B, then he says what is manifestly untrue.  It is not, however, until the last two or three pages that Diderot sets forth his dissent in its widest form.

“To refute Spinosa,” he says at last, “all that is necessary is to stop him at the first step, without taking the trouble to follow him into a mass of consequences; all that we need do is to substitute for the obscure principle which he makes the base of his system, the following:  namely, that there are several substances—­a principle that in its own way is clear to the last degree.  And, in fact, what proposition can be clearer, more striking, more close to the understanding and consciousness of man?  I here seek no other judge than the most just impression of the common sense that is spread among the human race....  Now, since common sense revolts against each of Spinosa’s propositions, no less than against the first, of which they are the pretended proofs, instead of stopping to reason on each of these proofs where common sense is lost, we should be right to say to him:—­Your principle is contrary to common sense; from a principle in which common sense is lost, nothing can issue in which common sense is to be found again.”