Are We Really Here?


One question that has always anguished me since we discussed it in a philosophy class I took a couple of years ago is how do we know that we are not a brain in a vat--or, more generally, how do we know that the external world exists and that our senses give us a generally accurate perception of it? Isn't that required to, for instance, read the Bible and thus have accurate knowledge of God?

Also a related question is how do you know others have minds like ours. I would tremendously appreciate good scriptural insight on these issues from a Reformed perspective.


At my age, it's good to see the old "chestnuts" from Intro to Philosophy are still in vogue - the "brain-in-the-vat" conundrum, as well as The Problem of Other Minds, mentioned in your follow up question. There is a good reason beginning students of Philosophy are confronted with these puzzles early on - it's an exercise in getting the students to question their most basic assumptions and presuppositions as they make their first forays into the subject of epistemology, which is the science of knowledge, or to put it more simply, "how we know what we know." There are several ways of looking at your question, so let's look at a few of them, going from the more simple "solutions," to the more complex.

One approach, popular among most "non-philosopher" types, is to look at beliefs in an external world, sense perception, and other minds as properly basic, that is, that the truth of these beliefs is so manifestly obvious and self-evident as to require no justification on the part of the believer. In this view, you don't have to defend your belief that you have a body, hands, feet, etc., or that there are others, similarly equipped, who enjoy the same experience. You are entitled to believe these things without any accompanying explanations. Sometimes this is referred to as naive realism, without the usual pejorative meaning of the word "naive." This is the ultimate example of WYSIWYG (What You See Is What You Get) and I suspect that the vast, vast majority of people would give you this "common sense" answer, whether they were familiar or not with the terms "properly basic" or "naive realism." And this, in large part, is why "normal" people look at those of us who study such things as more than a little suspect. And speaking of "suspect," I suspect from your question that you are not satisfied with such an answer, as many are not. They're looking for a "bulletproof" argument for sense perception, the existence of other Minds, and more importantly, the existence of God, so let's look at the approach a famous Rationalist philosopher (Rene Descartes) used.

Descartes is most famous for his "radical doubt," a determination to doubt the existence of everything that could possibly be doubted, and then see if a rational superstructure could be built on anything that remained. After spending a day in contemplation, Descartes determined it was possible to doubt the existence of absolutely everything - except his own existence. To doubt requires the existence of a "doubter," and concluded that "I think, therefore, I am (cogito ergo sum)."

Once he had established the "certainty" of his own existence, Descartes used a variation of Anselm's ontological argument for the existence of God (one can either conceive of an existent most perfect being, or a non-existent most perfect being, but since existence is "more perfect" than non-existence, it is only possible to conceive of an existent "most perfect being," therefore, God exists). From his own existence, and the existence of God, Descartes reasoned that our sense perception and understanding of the world is essentially true. Why? Because God is not a Deceiver, and would not permit "brains-in-a-vat" to believe that they were otherwise.

Now, there are quite a few Reformed thinkers who find this argument, at least part of it, to be a satisfactory answer to your questions. But a careful look at the argumentation reveals problems, at least to some. For example, while I find the Ontological Argument to be compelling (and it does have many prominent defenders) there are many philosophers who do not. They would point out that it doesn't prove the existence of God as He is portrayed in the Bible, and in fact find the definition "most perfect" to be problematic, especially whether it is "more perfect" to exist than to not exist. (As a rejoinder, I would point out that this objection is covered in the definition: Most perfect BEING). Further, some would point out that Descartes "presupposed" the existence and validity of Logic and failed to properly "doubt" its utility in his argumentation. In fact, in the history of philosophy, there never has been an airtight proof for the existence of the outside world, or the existence of other minds, which has led some to belief in various forms of Solipsism, the questioning of the existence of other minds, or in its "softer" versions, the impossibility of ever really knowing what other minds are thinking, feeling, or experiencing. (The popular philosopher Ayn Rand would have disputed this, which is why she called her school of Philosophy "Objectivism").

I hope, after reading so far, you aren't feeling terribly "anguished," about not having a rock-bottomed, copper sheathed "proof" for the outside world, and the existence of other minds, but keep in mind that every world view, whether theistic, atheistic, rationalistic, positivist, etc. has the same "problem." Every world view has to begin with some kind of "presupposition" in order to get what I personally refer to as "epistemic traction." Does this mean that, epistemologically speaking, all world views are equally valid? A Christian philosopher by the name of Cornelius Van Til would definitely have answered "no."

It was Van Til's contention that only Christian presuppositions (specifically, a belief in the God of the Bible) provided a coherent basis for the belief in anything, whether it be ideas like mathematics, Logic, ethics, the reality of the outside world, the existence of other minds, and even the possibility of human predication (to say anything meaningful whatsoever). Think about it for a moment: An atheist has to presuppose the existence and validity of Logic to get his "epistemic traction" and his world view moving, but since he believes the universe came into existence via a non-rational agency, he has no reason to think that Logic is true, or that his mind is able to give true information about the world around him. He grounds his belief in Logic in an incoherency, because the existence of the universe, and its accompanying "Laws," are uninterpreted "brute facts." They simply "are."

The Christian, on the other hand, begins with a coherent presupposition (God), and it is that presupposition, and only that presupposition, that forms a coherent basis for a belief in anything, to make knowledge of the outside world possible, and yes, to be able to understand God's word as it appears in Scripture.

There are some Reformed thinkers who believe Presuppositional Apologetics to be the only legitimate apologetic for the Christian. I will leave that determination for others, but in the meantime, I recommend to you a few books. The founder of Third Millennium Ministries, Dr. Richard Pratt, wrote a short paperback on Presuppositional Apologetics, entitled Every Thought Captive: A Study Manual for the Defense of Christian Truth, and you can order a copy through our e-store online at this website.

Dr. Pratt's professor of Apologetics at Westminster Theological Seminary, John Frame, has also written a somewhat more advanced treatment of the subject: Cornelius Van Til: An Analysis of His Thought, available through Presbyterian and Reformed Publishers. Dr. Frame was a student of Van Til, as was the late Greg Bahnsen, who wrote Van Til's Apologetic: Readings and Analysis, also available through P&R Publishers.

The readings get progressively more difficult as I've listed them here, but I highly recommend Presuppositionalism as a way to address the questions you've raised. I think in the end you will find it to be the most satisfactory answer.

Answer by: Larry Gwaltney, on behalf of the staff at IIIM. The opinions expressed by the author are not necessarily the "official position" of Third Millennium Ministries.

Answer by Dr. Richard L. Pratt, Jr.

Dr. Richard L. Pratt, Jr. is Co-Founder and President of Third Millennium Ministries who served as Professor of Old Testament at Reformed Theological Seminary and has authored numerous books.