 As with other transcendental errors, we can subreptively conflate a subjective principle generated by our intellects and of only regulative use to one that is objective, a real being not constructed in thought, but discovered through thought. Such, we may say, is the source of error in Spinoza’s use of substance and in other monistic metaphysics. Our construction of the ens realissimum has the appearance of an actual unity since it is the concept of the sum total of all positive predicates. This appearance then casts an illusion unrecognized by the metaphysicians, leading them into the subreptive error.