Universals exist as such only in the mind, not in external reality.
It may therefore be objected that, on this basis, demonstration does not impart knowledge of anything that actually exists; rather, it conveys notions merely posited in the mind, the realization of which outside the mind is unknown. If no knowledge of a real entity is obtained thereby, demonstration affords no knowledge of what exists and is thus of very limited benefit—indeed, of no benefit at all.
Yet the logicians themselves do not admit this. Instead, they employ demonstration in order to ascertain extra-mental realities, both natural and metaphysical.
The truth, however—as we have explained elsewhere—is that most questions in natural philosophy concern matters that are not necessary universals but hold only for the most part; such matters do not satisfy the aim of demonstration. As for theology, the universals they propose are even more unsound than those of natural philosophy, and the bulk of their discourse consists of false conjectures, far from the truthful propositions required to construct a valid demonstration.
For this reason we have been told, through a reliable, continuous chain of transmission, about the most eminent logician of his time, al-Khunji, author of Unveiling the Secrets of Logic, The Concise Summary, and other works. At the moment of death he is reported to have said:
“I depart this world having learned nothing, save my awareness that the contingent depends on an originator.”
He then added, “Dependence is but a negative relation; therefore I die knowing nothing.”
We have been given similar reports about another of their distinguished figures.
Anyone who has dealt with them knows this well: they are the most ignorant people on earth regarding the paths by which rational and transmitted knowledge are attained—except for those among them who acquired learning by some route other than their logical method. In such cases, their knowledge came from that alternative path, not from the logicians’ own procedure, despite their exhausting labor over the ‘demonstration’ by which they claim to weigh the sciences. Whenever one of them is recognized for any branch of learning, it is never by virtue of the rules they have codified in logic.