At its heart, Meditations on First Philosophy is the outline of a new epistemology that breaks with centuries of the scholastic tradition associated with Plato and Aristotle. The real question at the core of this epistemological divide comes down to the mechanics of the acquisition of knowledge. More specifically, how can actual knowledge be differentiated from ideas which are actually mere beliefs and not knowledge?
Rene Descartes specifies exactly what he means by the concept of “ideas” by asserting in Meditations on First Philosophy that it is be viewed as a term intended to “stand for whatever the mind directly perceives.” Ideas as thus defined as perceptual constructs which are subject to deception and thus not capable of being accepted as genuine truth or knowledge. The key to separating the apprehension of knowledge from the mere perception of ideas lies is determination of the origination of ideas.
Ideas which originate only from individual perceptions are to be doubted since they are only representations of reality rather than an actual mode of thought capable of producing truth and knowledge. These are the kinds of ideas produced by fantasies or within dreams and which are not dependent upon received stimuli from the outside world. The point of raising this objection is the fundamental allowance that the mind has a exhibited capacity for producing an illusion of reality every bit as strong within the dream world or the mind of the delusional fantasist as the reality that one perceives around them during their most lucid waking moments.
The same doubt must be applied to those ideas are received from outside the self which are subject to the prejudicial influence of the senses during those lucid waking moments. For Descartes, the ideas perceived as real in a dream and the ideas perceived as real when awake are essentially of equal value for the apprehension of knowledge. Mermaids can be consciously constructed by the imagination, for instance, yet this constructed idea produces no more empirical knowledge about the truth of mermaids than images of them produced by an unconscious mind creating dream imagery while asleep. Even seemingly empirical truth is still subject to perceptual skepticism. This type of idea can be illuminated through the example of the unclear visual perception of indistinct shapes in the distance which might prove to be people or might prove to be animals or might prove to be inanimate structures. The point is that ideas which originate outside the self based on received sensory input are also subject to challenge by Descartes as ideas which equate with actual knowledge.
The only ideas which are deemed worthy of producing actual knowledge for Descartes are those with which humans are innately endowed at birth. These are ideas which do not originate from outside the self, but neither are produced by individual mind. These innate ideas exist independent of the quality of perception and are essential and irrefutable truths: that a circle is round and that 2 plus 2 equals 4. Innate ideas are endowed with the properties of perfection that cannot be created by the imperfect minds of human beings and do not exist in our experience of the world around us. If such be the case, then the question that must be answered comes back to the issue of origination. From where do these innate ideas capable of producing knowledge originate if not from the imagination or experience?
For Descartes there is only one rational answer: they are proof of the existence of God. Since innate ideas are the result of human beings and since all human beings apprehend these ideas as knowledge, an outside agency must be responsible for their existence. Thus, acquisition of knowledge as a foundation of the philosophical thought of Descartes is founded upon and bound to the intervention of a perfect supreme bring.
