Descartes and Heidegger both set a new standard for thinking, but at completely different ends. Descartes says a subject is a thinking thing that is not extended, and the object is an extended thing which does not think. Heidegger rejects this distinction between subject and object by arguing that there is no subject distinct from the external world of things because Dasein is essentially Being-in-the-world. To Heidegger, everything has an essence, yet that essence is concealed to humans.

Descartes’s philosophy placed a heavy emphasis on deductive reasoning and mathematics. He developed analytic geometry and the Cartesian coordinate system which helped scientists use mathematics to model the physical world. One of his influences on today’s world is his philosophy of mind, dualism, where the mind is a nonphysical substance. Descartes proposed that reality consists of two separate realms: a physical realm and a mental realm. The physical realm is the realm of matter and energy. Its properties can be measured and studied by science. Everything in this realm operates only by mechanical properties. Descartes included the body as part of the physical realm, viewing it as a biological machine with no free will.

Descartes’s view that the body is a machine has led a mechanical approach in medicine, because Descartes views technology as separate from ethics. This idea is prevalent in today’s philosophy – computer science majors are not required to take a morality course. This means technology is being developed without ethics. This is a dangerous stance. As Heidegger points out, “everywhere we remain unfree and chained to technology, whether we passionately affirm or deny it.” Therefore, ethical technology needs to be addressed. But to address this issue, one must also consider how humans arrive at technology in the first place.

Epistemology is the theory of knowledge. It addresses four main questions: (1) What is knowledge; (2) how is knowledge acquired; (3) what do people know; and (4) how do we know what we know? Descartes tried to answer these questions by using reason. Heidegger however dismisses epistemology since it is rooted in ancient ontology, which dominates Western thinking. His focus is on the meaning of Being.

Descartes sees reason as the primary source of knowledge. Reason is defined as “a basis or cause; a statement presented in justification or explanation of a belief or action; to form conclusions, judgments, or inferences from facts or premises; to think through logically.” He believed reason could be used to find certain truths if used correctly. But one must ask how can technology be based on a logical deduction, if no ethics is applied?

Descartes’ answer to this question is flawed. He dismisses John Locke’s assertion that the mind is a blank slate at birth; all knowledge stems from experience. Descartes believes there is a certain something—native intellect or reason—that all are born with and all share. He believes people are equally human, so all must be equally rational. He argues that while people have different opinions and arrive at truths with varying degrees of success, this is not because some are better equipped with reason than others, but because different people apply reason in different ways. Heidegger would argue that humanity is on its way to an arrival, but not a pleasant one. A reorienting of man is the only way that nature will reveal itself. And this reorientation is the only way humanity can establish a relationship with the world that is not ultimately self-destructive. In this thought, Heidegger dismisses Descartes idea that all humans are equally rational. As Heidegger sees it, humanity has an exaggerated sense of power it thinks it possesses over nature, which will lead to humanity deeming it has control over all existence. Narcissism is not a rational truth.

So then if humans are not to wield power over all, what is man’s purpose? Descartes uses his reason to explain human existence. The fact that Descartes doubts suggests that he must exist, or else he would not be able to doubt. He concludes: "I am thinking, therefore I exist." His knowledge of this claim is a "clear and distinct perception;" it is not something that he learns through reasoning – but something that he knows because he is incapable of doubting it. Descartes concludes that he is essentially a thinking substance, and that his soul is distinct from his body. Descartes, wanting to avoid a theological debate, conveniently next arrives at the idea of God, even though Descartes previously said not to believe in anything that can be doubted. Descartes places God in his philosophy as merely setting the world in motion.

Descartes believed self-existence was the foundation which man must build all subsequent knowledge. In Descartes’ analysis, he says one must find something that cannot be doubted; which is impossible, as anything can be logically doubted. Since one knows his existence, and has ideas, the one can logically deduce that his ideas also exist. If ideas exist, then something caused these to exist. Since this idea is greater than self, there must be a perfect being (God) who caused this idea. And if there is a perfect God, one can logically deduce that a perfect being would not give deceptive faculties. Therefore, he concludes humans possess distinct perception. By Descartes analysis, humans do not have deceptive faculties; humans can trust their senses with certainty.
In short, Heidegger's dissects this Cartesian thinking in hopes to destroy the traditional visual metaphor for truth (as in Plato’s Republic). According to Heidegger, the problem with Descartes' view and the traditional thinking is that they turn knowledge into method. Heidegger distinguishes between knowledge derived from calculative thinking and that which comes from meditative thinking. It is meditative thinking that is appropriate to philosophy. According to Heidegger, man is a thinking, meditating being – not just a thinking substance.

It is this meditative thinking that will answer humanity’s orientation to technology, not the Cartesian reason. And this orientation will help man understand what its purpose is in relation to technology. Heidegger says from the start why understanding this orientation is so important, "The will to mastery becomes all the more urgent the more technology threatens to slip from human control.” Therefore, man needs to consider technology as a means to an end and as a human activity.

So what is meant by technology? Heidegger uses Greek technikon (techne), which is a type of knowing. "What is decisive in techne does not lie at all in making and manipulating nor in the using of means, but rather in the revealing mentioned before” (Heidegger). Therefore technology’s essence is a mode of revealing. According to Heidegger, modern technology does not draw energy, but extracts it, which is an exploitation of the Earth. More directly, nothing has intrinsic value – it is only good for something. Heidegger here differs from Descartes. Heidegger does not think that humans are just machines. He makes note of the expression human resources, saying that this aligns humans with materials such as coal. Heidegger does not believe man can be a raw material as man has the power to destroy nature.