The first step on the path of realism is to recognise that one has always been a realist; the second is to recognise that, however, much one tries to think differently, one will never succeed; the third is to note that those who claim that they think differently, think as realists as soon as they forget to act a part. If they ask themselves why, their conversion is almost complete.
Most people who say and think that they are idealists would prefer to be able not to be such, but they cannot find out how. People tell them that they will never get outside their thought and that anything beyond thought is unthinkable. If they consent to seek a reply to this objection they are lost from the start, for all the idealist’s objections against the realist are formulated in idealist terms…
We must begin by distrusting the term ‘thought’; for the greatest difference between the realist and the idealist is that the idealist thinks, whereas the realist knows…
[For the idealist] the spirit is what thinks, while for us the intellect is what knows… An idealist term is generally a realist term which designates one of the spiritual conditions of knowledge, but is not considered as generating its own content.
The knowledge of which the realist speaks is the lived and experienced unity of an intellect with an apprehended reality. This is why a realist philosopher always presses towards the very thing that is apprehended, without which there would be no knowledge. The idealist philosophers, on the other hand, since they start from thought, very soon choose as their object science or philosophy. When he genuinely thinks as an idealist, the idealist embodies perfectly the essence of a ‘professor of philosophy’; while the realist, when he genuinely thinks as a realist, fulfils the authentic essence of a philosopher; for a philosopher talks about things, but a professor of philosophy talks about philosophy.
Just as we do not have to go from thought to things (knowing the enterprise to be impossible), so we do not have to ask ourselves whether something beyond is thinkable. It may well be that something beyond thought is not thinkable, but it is certain that all knowledge implies something beyond thought. The fact that this something-beyond-thought is given to us by knowledge only in thought does not prevent it from being something-beyond; but the idealist always confuses ‘being given in thought’ and ‘being given by thought’. For one who starts from knowledge something-beyond-thought is so far thinkable that it is only this kind of thought for which there can be a ‘beyond’.
The realist will be committing an error of the same kind [as the idealist] if he asks himself how, starting from the ego, he can prove the existence of a non-ego. For the idealist, who starts from the ego, this is the normal, and indeed only possible, formulation of the question. The realist must be doubly wary; first because he does not start from the ego, and secondly because for him the world is not a non-ego (that would be nothing at all), but an in-se. An in-se can be given in knowledge; a non-ego is what the realist is reduced to for an idealist, and it can neither be grasped by knowledge no proved by thought.
Etienne Gilson, Methodical Realism, quoted in E.L. Mascall's The Openness of Being [p.93-94]
E.L. Mascall adds the following comment:
For Gilson, the idealist problem, how we can compare the content of our mind, with the reality outside in order to know what degree the former accurately depicts the latter, simply does not arise. It is an insoluble problem which idealism has created for itself; for the realist, there is no such thing as a noumenon in the idealist's sense of the term.
~ Jakian Thomist