If it were not for what Descartes writes later, we might conclude that he thinks that we are nothing but minds. That inclination counteracts the temptation to subordinate the body to the mind and to reduce physical objects only to how they are known in terms of mathematical, quantifiable physics. For the Descartes of the early Meditations, the objects we see are not the objects we know , because what we know is intelligible only in terms of the clarity and precision of the formulas of physics. That is why information provided by the senses cannot be the basis of knowledge. But as feminist theorists observe, Descartes' later work shows how our bodies are essential aspects of ourselves which cannot be discussed in terms of certainty and knowledge without seriously misunderstanding how the body is essential for defining ourselves as human.
Introspection reveals the reality of mental things that are accessible only privately.
Because the mental and the physical can be conceived as distinct, it is possible that they are distinct. Responses to the objection about interaction in particular have been quite ingenious. Some philosophers decide that the way to resolve the difficulty about freedom is simply to deny that human beings are free or to deny that the mind or soul is any thing at all. This kind of reduction of mind to something material or to a function of something material worries some contemporary philosophers who trace the origin of such an approach back to Descartes. Even though Descartes argues that the mind and the body are two different kinds of reality, he opens the door for a reductionist approach by suggesting that bodies be treated in a measurable, quantifiable way.