He would lay hold of anything "if it had but the force of authority," rather than have none.
Accordingly Aquinas prepared himself on this side by commentaries on Aristotle's De Inter pretatione, on his Posterior Analytics, on the Metaphysics, the Physics, the De Anima, and on Aristotle's other psychological and physical writings, each commentary having for its aim to lay hold of the material and grasp the method contained and employed in each treatise.
It would seem that the perception intended to constitute the standard of truth is one which, by producing a mental counterpart of a really existent external thing, enables the percipient, in the very act of sense, to " lay hold of " or apprehend an object in virtue of the presentation or sense impression of it excited in his own mind.