"esse est percipi" ("to be is to be perceived") - George Berkley.
"And he said to him, “You shall love the Lord your God with all your heart and with all your soul and with all your mind." (Matthew 22:37)A popular and recent epistemology that has made inroads in the secular world is Idealism, the theory that reality is the product of the human mind, and that nothing can be known that is independent of the mind. Such a basis for knowledge is the height of autonomy, and although some Christians are drawn into some strands of Idealism, one has to wonder if these can maintain an Orthodox view of Creation. There are several subcategories of Idealism, but all of them have in common the belief that reality is dependent solely on the preception of the mind.
The human mind is indeed an awe-inspiring entity. Indeed, the most challenging study that the mind can undertake seems to be the study of itself. Seeing as how we know so little about the mind, on what authority would anyone claim that it can be the basis for reality? Idealist Immanuel Kant asserts:
"...if I remove the thinking subject, the whole material world must at once vanish because it is nothing but a phenomenal appearance in the sensibility of ourselves as a subject, and a manner or species of representation." - Critique of Pure Reason A383However, it does not follow that, because the preception of an object exists in the mind, that existence of that same object is dependent upon the mind. Idealists assume, without any justification, that the essense of any object is only in it's perception, thus equating the separation of mind from matter with the separation of perception from existence. Of course, having the human mind as the ultimate source of reality poses several problems:
1. Idealism cannot consistently distinguish between, hallucinations, dreams and reality.
2. Idealism can neither allow for not account for mistakes in "perception", mistaken identity, optical illusions, the sounds of the ocean inside of a seashell, etc. since reality is based upon perception. There is nothing outside of the mind by which we may validate the accuracy of our ideas, including other people's ideas.
3. Idealism cannot justify any objective truth claim, but rather results in Subjectivism in both Epistemology and Ethics (Whose mind contains actual knowledge of these things? What about minds that disagree with each other?)
As amazing as the mind is, it is not autonomous. God is sovereign over the mind (Deuteronomy 28:28, 1 Kings 3:9, 2 Thessalonians 2:11). The mind itself cannot exist unless it is created by God, and can only reason and think as a reflection of what God thinks and reasons. As fallen creatures, our minds are by nature at enmity with God (Romans 8:6-7), and thus need to be renewed (Romans 12:2). While the mind is an important means by which knowledge may be obtained, it cannot be, in and of itself, the basis for either knowledge or reality.