Believe it or not there once was a popular song with this title. Of course, they were not singing about Rene Descartes the philosopher. I chose this title because there is a real sense in which it applies to the epistemological efforts of Rene Descartes. He started by trying to find out if there is anything we can know as absolutely certain and ended up in a bit of a mess from which he could not walk away. Here’s how his thinking went. (Meditations on First Philosophy)
What is needed is an absolutely certain beginning point from which we can ascertain whether there is anything else we can know with absolute certainty. He set aside any knowledge he thought he had as a result of sensory perception because it is always subject to error. Rather, he took as his point of departure the statement “I think, therefore I am.” He next reasoned that there is no way he could be mistaken about this proposition because even to think that one is wrong, or to be wrong, requires one’s existence. So now he argued that he knows he can trust his reasoning powers because they establish at least one true belief.
From this starting point Descartes went on to reason that since he can trust his reasoning powers whatever presents itself as “clear and distinctly true” must be so. He next reasoned that he cannot deny the existence of God because he as a finite being could never come up with the idea of an infinite being, namely God, Thus God must exist. These ideas Descartes concluded he could affirm because they presented themselves to him “clearly and distinctly”, therefore he went on to concluded that whatever ideas present themselves to his mind clearly and distinctly can be trusted to be true. Therefore, the idea of God must entail God’s existence because the opposite would involve a contradiction, since God is by definition perfect and would not be so if he did not exist.
He also affirmed the existence of matter, namely his own body, because its reality presents itself to his mind “clearly and distinctly. People then can be said to consist of two sorts of reality, namely minds and bodies, although these two realities were in Rene’ view entirely distinct, the one being mental and the other being physical. This presented a serious, and in the end, fatal problem for young Descartes, because at first he could not think of any way to coordinate and integrate these two types of reality.
He did finally come up with a theory as to how the two realities could be understood as existing in one and the same person. He had heard of the existence of the “pineal gland” deep within the brain, and he reasoned that within the brain these two realities somehow intersected so as to enable our thoughts and our gland there was a kind of swivel which was somehow moved by the mind’s thoughts, much as the wind moves a windmill, thus causing the body to respond appropriately. I think of moving my arm and these winds cause the muscles in my arm act correspondingly.
Thus Descartes was unable to explain how the action might work in the opposite direction. Moreover, there was no explanation for how to bring these two aspects of human reality together. So, there was Rene Descartes, a truly great mind, stuck with an unexplainable dilemma. He could not explain how these two obviously real aspects of human life could be coordinated. This was a logical difficulty from which Rene could not walk away. He was destined, in the minds of subsequent thinkers, to remain fundamentally a dualist, unable to explain the relationship between mind and matter.
Two thinkers who followed in Descartes’ Rationalistic tradition, Spinoza and Leibniz, each settled the matter by affirming that mind and matter are simply two sides of the same reality, Spinoza collapsing mind and matter into one substance (Ethics) and Leibniz doing the opposite (Monadology). One might conclude that neither of these other two Rationalist thinkers hardly really solved Rene’s dilemma. Perhaps they must all walk away.

The pre-Socratic philosopher Parmenides (c.500 BCE) had a disciple named Zeno who worked at proving Parmenides’ theories to be true. He offered four paradoxes with which to prove that the idea of change and sense perception are logical fictions. His main contention was that the idea of motion is illogical. See what you think of his reasoning.
1. Motion is illogical – because for it to exist there would have to be an infinite amount of time for a runner, for instance, to traverse a given amount of space. But no matter how long one has the given distance to be covered would have to be subdivided an infinite number of times, thus taking an infinite amount of time to do so. Thus motion itself is an illogical notion.
2. Similarly, if we give a very slow tortoise a tiny head start his opponent, a rabbit, no matter how long the race course and how fast the rabbit is, the rabbit would never be able to catch the tortoise because it would first have to cover half the distance between himself and the tortoise while the tortoise would have time to inch ahead a tiny amount, ad infinitum! So, the idea of motion is illogical.
3. Again, if an archer shoots an arrow into the air no matter how fast the arrow goes it will never be able to reach the target because it would first have to traverse half of the distance to the target, and each inch of this distance is subdividable into logically dividable parts, thus requiring an infinite amount of time for the arrow to cover those parts. Thus, the idea of motion is itself contradictory.
4. Finally, the idea of motion is self-contradictory because it requires an infinite amount of both time and distance for any movement to take place. So, motion itself is impossible because would require an infinite amount of space and time in order to be real.
Clearly, these puzzles posed by Zeno somehow miss the
point since we all know that time and space are in fact divisible and motion is neither impossible or self-contradictory. So wherein lies the solution to Zeno’s paradoxes? Both time and space are real yet these paradoxes seem to call them into question.
Surely our senses do sometimes deceive us concerning how far away something is, or how fast something is moving. How, then, are these puzzles to be explained? One way to explain them is to point out that these puzzles trade on the idea that the concepts of space and time are always relative to some system or other, and thus do not exist in and of themselves as abstractions.
Zeno’s paradoxes trade back and forth on the difference between the abstract concepts of space and time, on the one hand, and their actual use in everyday life. One might turn the tables on him by suggesting that his own spoken words must be meaningless because they are divisible since they are spoken one at a time and not all at once.