As used today, the word realism means in the first place the opposite to idealism when it claims that it is possible to pass from the subject to the … - Étienne Gilson

What, then, will this philosophy be? Thomas only employed it for the service it renders Christian wisdom. No doubt this is why he never thought of separating it from this wisdom and giving it a name. He probably did not foresee that the day would come when people would go through his works to extract the elements of a philosophy from his theology. He himself never attempted this synthesis.

Every given reality implies the thought which apprehends it. Therefore being is the condition of knowing; knowing is not the condition of being.

Indeed, all idealism derives from Descartes, or from Kant, or from both together, and whatever other distinguishing features a system may have, it is idealist to the extent that, either in itself, or as far as we are concerned, it makes knowing the condition of being.