Rene Descartes and John Locke attend a social event in a large mansion. As the men socialize, the host recommends the two have a look in the home's library. Escorting them in, the men turn their backs to the door, studying the shelves of books. There is a great selection, among them being the works of Plato, Aristotle, and the likes of many others. As the host excuses themselves, they close the door and it seals with a quiet click. Descartes and Locke have presumably been locked in this room. Here then begins their discussion of escape, freedom, knowledge and God.

Locke: If I did not know better, I might assume that we’ve been locked in this room by our thoughtful host.
Descartes: How great, the gift of perception. 
Locke: Or, how great the gift of opportunity. Many have made note not to look such a horse in the mouth.
Descartes: And what do you mean by this?
Locke: We have been presented the unique opportunity of forging our escape. Never have I been in such a situation, therefore I will gain a multitude of experience through this. 
Descartes: Son, you have the God given ability to protect yourself. 
Locke: We are born into the world, new and fresh, a clean slate. No knowledge of how to keep ourselves safe. 
Descartes: It is an innate gift, your understanding of what a thing is, what truth is and what thought is.
Locke: Yet my understanding of what a thing is does not keep me safe nor is it able to protect me. This I can only know by experience. When we may observe in our natural faculties, fit to as easy and certain knowledge of them as if they were originally imprinted on the mind.
Descartes: Ah yes, as if they were predetermined to be experienced. As if these gifts were bestowed by a greater power and determinately, a God. For our faculties lay within our souls which are separate from the bodies we experience with. 
Locke: How can we conceptualize without being familiarized with the concept originally? We may have the ability to perceive our outer world but we may only know a thing by processing it with our senses, know a truth by seeing it work, and know a thought by sentience. 
Descartes: Hm, allow me to turn this over in my mind. 

Descartes approaches a bookshelf, his finger brushing over finely dusted spines until he lands on a copy of Plato's Republic.  

Descartes: Do you know what Plato's thoughts are on the human soul? 
Locke: I am familiar but for your sake please, refresh me. 
Descartes: Plato believed in the soul. He believed the soul is what separated us from animals, any other form of life. The soul is perhaps this sentience you speak of. 
Locke: A soul, even as the validity of its existence is unclear to me, is not a replacement for the mind. It is redundant to see ourselves as no more than an amorphous metaphysical force guiding our bodies and storing all of our inner mental functioning. This is not sufficient enough to prove our ability to process and perceive as human beings. I agree with Plato that there is a distinction between animal and man, yet that distinction lay in the mind and its capabilities. 
Descartes: Perhaps we should return to the idea of a God. The idea is only permissible by God himself, to synthesize something so much larger than ourselves. In the same way we cannot experience the infinite but we can grasp its concept. Not to be confused with the indefinite which are things which simply have no clear end. A thing may go on for an inconceivable amount of time but we remain with the understanding that there is an end. There is no start or end of God and our ability to conceive a supremely divine being cannot be one learned through experience. For there is no perfect being which we will encounter such as a God. This image is imprinted by God himself, we are given the capabilities to conceive such greatness. The idea of a God has been carried throughout times and cultures, in forms all deductive of a God. 
Locke: There are populations who are exempt from this imprinted knowledge you speak of. A child or an idiot knows not of a God, For if they are not notions naturally imprinted, how can they be innate? And if they are notions imprinted, how can they be unknown? To say a notion is imprinted on the mind, and yet at the same time to say that the mind is ignorant of it, and never yet took notice of it, is to make this impression nothing. An infant cannot yet communicate yet you believe it has the capacity to understand complexities such as a God. An idiot has not the capacity to care for itself, but has an innate ability to discern danger. We know this cannot be. 
Descartes: There are many things we do not know, many of which empirical evidence does not provide us answers to. Matter, mind, and God are only quantifiable by spatiotemporal dimensionality. There are patterns within our existence that are resistant to space and time, which we cannot truly fathom yet cannot be denied. Our sensory capacities are passive and our perception is out of our control. This is the link of all humanity. My experience is not seeing the color green but having light reflecting from the backs of my eyes allowing me to perceive the color green. Children and idiots may be outliers but they are not so far removed they have no capabilities of perception. Mind and matter simply depends on God's will. 
Locke: We directly access the truth through experience and our ideas are merely finite because there are only so many experiences to be had, and with only so much life to live, there is no way to access it all. Even the truth itself is subjective on the basis that we have very little to certify what is true. It is to our benefit that we have a wide array of experiences to provide us with a broader knowledge so we can navigate life with ease. I still say, these experiences are inaccessible to children and idiots. They cannot conceive their own perception or what an idea is. They are not able to understand the technicalities of our existence, for they have no idea the color is seen through refraction. To think on such a level is a luxury. 
Descartes: The inner awareness of ones thought and existence is so innate in all men that although we may pretend that we do not to have it if we are overwhelmed with preconceived opinions and pay more attention to words other than their meanings, we cannot in fact fail to have it. Thus when anyone notices that he is thinking and that it follows him from this that he exists, even though he may never before have asked what thought is or what existence is, he still cannot fail to have sufficient knowledge of them both to satisfy himself in this regard.
Locke: So you mean to say, to have internal awareness is to know existence? 
Descartes: Yes. You need not demonstration to know you are alive.
Locke: Let us return back to the room we are in. We seem to have forgotten the situation at hand. Is touching this wall not a demonstration of my existence? I am solid, real, and unchanging. That is in part undoubtedly the knowledge to know we exist. 
Descartes: Our senses are deceptive. Nevertheless, when deception occurs, we must not deny that it exists; the only difficulty is whether it occurs all the time, thus making it impossible for us ever to be sure of​​ the truth of anything we perceive by senses. 
Locke: So who is to be able to differentiate between these deceptions. How is it possible to identify reality from dreams? Who is to say I am not dreaming up this scenario, that the door is not locked and I have been free this entire time? 
Descartes: But we do not dream all the time, and for as long as we are really awake we cannot doubt whether we are really awake or dreaming. And further more, the senses are quite passive and report only appearances.  You can feel the wall is solid, see the doorknob is gold and feel the pressure of a lock in place. These are merely the physical. 
Locke: Shall I give it a test then? See if we are trapped within a prison of our minds rather than our friends doing?

Locke reaches for the door handle, cool and undoubtedly round. He twists the knob and meets no resistance. The door clicks open just as it did when it shut. 

Descartes: It appears we’ve gotten far ahead of ourselves. Perhaps there is something to the experience after all. 



Citations:
René Descartes, Meditations on First Philosophy, trans. John Cottingham (Cambridge: Cambridge University Press, 1996). 
 
John Locke, An Essay Concerning Human Understanding, ed. and abridged by Kenneth Winkler (Indianapolis: Hackett Publishing, 1996).