The Meditator reasons that all ideas are mere modes of thought, and in that sense they are all equal: they all have the same amount of formal reality, that is, reality intrinsic to themselves. However, what they represent differs greatly, and so their objective reality—the reality of the things they represent—also differs greatly. Thus, the idea of God has more objective reality than the idea of a tree, which has in turn more objective reality than the idea of the color red. Nonetheless, all three of these ideas are just ideas, and all have the same degree of formal reality. (The analysis section below will explain in more detail what is meant by "formal" and "objective" reality and what it means to have more or less reality.)

The Meditator asserts that no effect can have a greater amount of reality than its cause. That is, everything that comes into being must be made to be by something that has an equal or greater amount of reality. For instance, a stone can be made by chipping off a larger piece of rock, since the larger rock has more reality, but a stone cannot be made out of a color, since a stone has more reality than a color. The Meditator also suggests that an idea can only be caused by something that has as much formal reality as the idea has objective reality. The idea of a stone, then, could be caused by a stone or a large rock but it could not be caused by a color. The Meditator grants that ideas can be caused by other ideas, but that there must ultimately be something more than an idea that is the cause of these ideas. The first cause of an idea must be something with at least as much formal reality as the idea has objective reality.

If he can conceive of some idea with so much objective reality that it must come from some cause with more formal reality than he herself possesses, the Meditator reasons that he will then know that something outside his mind exists. His ideas of other people, animals, and angels can easily come from himself even if no such things exist. Similarly, corporeal things contain nothing so great that it could not originate in him. From the reasoning of the Wax Argument, he has concluded that he can only clearly and distinctly perceive properties like size, extension, shape, motion, duration, number, and substance when examining corporeal things. Most of these properties the Meditator himself also possesses. And even if, as a thinking thing, he may not have size, extension, shape, or motion, these properties are modes of the substance of body, and, as a thinking thing, he is a substance, and therefore has more reality than these modes. (Cartesian ontology, modes, and substances, will also be elucidated in the analysis.)

Sensible qualities like color, sound, smell, taste, heat, cold, and so on are only perceived in a confused and obscure way, and the Meditator is not even certain as to whether or not they are things or non-things. If they are things, they must have such a small degree of reality as to originate unproblematically from the Meditator himself.


This section of text dives right into a number of distinctions made by the medieval Scholastic philosophers that would have been very current in Descartes' day. Their currency has since waned and these terms are no longer familiar to the ordinary reader, so what follows will be a brief tutorial on Cartesian ontology and distinctions within the theory of ideas.

For Descartes, as for most thinkers of his time, the fundamental building blocks of reality are called substances. Substances can exist independently and are indestructible. In Cartesian ontology, there are two kinds of substances: bodies and minds. Of substances that are minds, there are finite minds, such as people and angels, and there is the infinite mind, God. Thus, when the Meditator asserts the sum res cogitans, he is asserting that, as a substance, he is a mind rather than a body.

All substances also have affections, things that hold of the substances. Affections are not substances themselves because they cannot exist independently of the substances that they affect. Affections can be divided between attributes and modes, and attributes can be divided between primary attributes and omni-generic attributes. Primary attributes are those attributes that explain the essence of the substance they belong to. According to Descartes, the primary attribute of body is extension and the primary attribute of mind is thought. Thus, all bodies are necessarily extended in space and all things that are extended in space are necessarily bodies. Similarly with minds and thought: all thinking things are minds, and all minds think. Omni-generic attributes are attributes that can hold of any substance and do not define their essence. Examples are existence, duration, and number. Modes are modifications of primary attributes, ways in which something can have a certain primary attribute. For instance, squareness is a mode of extension since it is a way in which a body might be extended. Similarly with color, size, other shapes, motion, etc., for bodies; and imagining, willing, sensing, feeling, etc., for minds.

Now we move on to the distinction between formal and objective reality. For Descartes and the Scholastics, ideas are the link that connect mind and world because they have both formal and objective reality. To clarify the distinction once more, formal reality is the kind of reality things have in this world and objective reality is the reality of the objects represented by different ideas. Thus, an idea can have formal reality, being a mode of thought itself, and it can also have objective reality, representing something outside of itself.

When Descartes speaks of things as having more or less reality than other things, we can understand him as roughly dividing up reality along a scale where infinite substances (i.e., God) have the most reality, followed by finite substances, followed by modes. As we mentioned earlier, finite substances are bodies and minds, while modes are modifications of body and mind, like color, shape, size, imagination, idea, will, etc. This implies, among other things, that ideas have the formal reality of modes, since they are modifications of mind. So, for instance, the idea of a car would have the formal reality of a mode (since it is an idea) and the objective reality of a finite substance (since the idea is of a car, which is a body). On the other hand, the idea of the fear of cars would have the formal reality of a mode (since it is an idea) and the objective reality of a mode (since the idea is of a fear, and fear is also a mode of thought).

According to Descartes, something with a certain degree of objective reality must ultimately be caused by something with that degree of formal reality. So, for instance, the idea of a car (which has the objective reality of a finite substance) might be caused by the idea of a bicycle, which only has the formal reality of a mode, but that idea of a bicycle might then have been caused by a bicycle itself, which has the formal reality of a finite substance. If we trace the causal chain far enough back, we will find a cause with as much formal reality as the idea has objective reality. If the Meditator can locate an idea that has more objective reality than he has formal reality, he can conclude that there must exist something outside of himself which had to create the idea. Since he has the formal reality of a finite substance, the only thing that has more reality is infinite substance. Thus, he will try to prove that something besides himself exists by contemplating his idea of God.

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