Early Modern Philosophy:
Descartes on Formal and Objective Reality


To see what Descartes is up to in Meditation III, it is important to understand what he means by some key terms.

Modes, Finite Substances, and Infinite Substances

One important distinction is that between substances and modes. A substance is basically a particular thing; thus, a tree, a rock, and a human body would all be substances. In addition to these substances, which Descartes would call material substances, he also thinks that minds are substances. Minds are thinking substances as opposed to material substances.

Now, substances have properties or characteristics, which Descartes often calls modes. The modes of a physical object ("material substance") would include things like its location in space and time, its shape, and its volume. The modes of a mind ("thinking substance") would include things like the specific ideas, judgments, and desires of the subject.

(In addition to the "modes" just mentioned, every substance has an essential property. Descartes thinks that the essential property of material substance is extension (i.e. occupying a region of space and time), and that the essential property of thinking substance is thinking. D seems to think of the modes I just mentioned as something like "modifications" or maybe specifications of, or ways of having, the essential property. So having ideas, believing, desiring, etc. are specific ways of thinking; having a certain shape or volume are specific ways of being extended.)

Now, rocks, trees, and human bodies are not only material substances, but finite material substances. Similarly, human minds are not only thinking substances, but finite thinking substances.

If there is a God, then God is also a substance, but not a finite one: God would be an infinite substance.

So we have three ontological categories here: modes, finite substances, and infinite substance.

Formal Reality

Descartes doesn't think of being real as a yes-or-no matter. Rather, some things are more real (have more reality) than others.

Formal reality is the kind of reality something has by virtue of the kind of thing it is. Modes, finite substances, and infinite substance(s) all have formal reality, but not to the same degree.

Modes have the least formal reality; finite substances have more reality than modes, but less than infinite substance(s); and infinite substances have the highest possible degree of reality.

The principle that determines how much formal reality something has seems to be one of dependence: the more dependent something is on other things for its existence, the less formal reality it has. Modes depend on finite substances but not vice versa (for instance, the shape of my hand wouldn't exist without my hand, but my hand could exist without having that specific shape; finite substances depend on other things for their existence, but an infinite substance wouldn't depend on anything else at all.)

For convenience, let's say that formal reality comes in three main degrees. Modes have the lowest degree, finite substances have a medium degree, and an infinite substance would have the highest degree.

Objective Reality

Finally, let's consider "objective reality."

There are two crucial things to realize about objective reality.

First, objective reality is possessed only by representations, that is, by things that stand for other things. Now the representations Descartes is primarily interested in are ideas. (Portraits and spoken or written words are also representations, and so presumably they would also have objective reality, but we'll ignore this and just focus on ideas.)

The second thing to understand about objective reality is this principle:

The degree of objective reality of an idea is the same as the degree of formal reality the object of the idea would have if it existed.

Let's abbreviate the high, medium, and low degrees of reality by H, M, and L. Then the idea of a dog has the M degree of reality (because it represents a dog, and dogs have the M degree of formal reality).

But equally, the idea of a unicorn has the M degree of reality. There are no unicorns, but if there were any unicorns, they would be finite substances, and so they would have the M degree of reality. And this is enough to give the idea of a unicorn the M degree of objective reality.

Similarly, all ideas of modes will have the L degree of objective reality, and all ideas of infinite substances will have the H degree of objective reality.

The Formal Reality of Ideas

One final twist: in addition to representing things, ideas are things: in particular, they are modes of thinking substances. Since every idea is a mode, every idea has the lowest degree of formal reality.

So it is crucial to keep formal and objective reality straight! The idea of a unicorn has the lowest degree of formal reality (because it's just a mode), but it has the medium degree of objective reality (because it represents a finite substance). Similarly, the idea of God, like every other idea, has the lowest degree of formal reality (because it's just a mode), but it has the highest degree of objective reality (because it represents an infinite substance).

Handy Chart

Here is a chart with some examples that may help to keep these ideas sorted out.

  Degree of Formal Reality Degree of Objective Reality
property of redness L (it's a mode) N/A (not an idea)
Elsa (my son's cat) M (she's a finite substance) N/A (not an idea)
Pegasus none? (Pegasus doesn't exist) N/A (not an idea)
God H (assuming God exists, that is) N/A (not an idea)
idea of redness L (it's a mode of thinking) L (represents a mode)
idea of Elsa L (it's a mode) M (represents a finite substance)
idea of Pegasus L (it's a mode) M (even though Pegasus doesn't exist,
the idea of Pegasus represents a
finite substance)
idea of God L (it's a mode) H (represents an infinite substance)


Last update: January 21, 2009
Curtis Brown  |  Early Modern Philosophy   |  Philosophy Department  |   Trinity University