Descartes’ Three Substances: A Philosophical Analysis
Descartes’ Three Substances
Descartes, through his method, seeks to prove the reality of substance. His conception is dualistic:
Thinking Substance (Res Cogitans)
This substance consists of thought, desire, feeling, and imagination. We may doubt the existence of our body and the external world, as information comes through the senses, but we cannot doubt the existence of our thoughts. Descartes classifies ideas as follows:
- Adventitious or acquired: These originate from sensory experience or teaching.
- Fictitious or artificial: These are invented by ourselves.
- Innate or natural: These emerge from our own thinking.
Divine Substance (God)
Descartes argues that our imperfect minds possess the idea of perfection. This innate idea of perfection cannot originate from ourselves; it must have been placed within our minds by a divine reality (God). This allows for a clear distinction and the existence of a reality external to our minds. This perfect substance would not allow the ideas within us to be an illusion. Therefore, the evil genius hypothesis is false, and the existence of the external world and our body is demonstrated.
Material Substance
We experience sensations of external objects. These sensations are caused by material objects (they are not a product of our imagination, nor placed in our minds by God). God allows us to use our senses, and when these are always subordinate to reason, they prevent us from being deceived. Besides the thinking substance, there is another type of substance: the body of the material world. Its key feature is extension (size, shape, movement). According to Descartes, objects have two types of qualities. The primary qualities are objective and therefore real. The secondary qualities are subjective, residing not in the object but in the subject that perceives them (color, taste, etc.).
Relationship Between Thinking and Material Substance
Human beings are formed by two different substances. Descartes argues that there is a point in our body called the pineal gland, located in the middle of the brain, where the soul resides and connects with the body.
Cartesianism influenced rationalist thinkers like Malebranche, Spinoza, and Leibniz. It also influenced empiricist Locke, as well as creators of philosophical systems like Kant and Hegel.
Nicolas Malebranche (Occasionalism)
Dissatisfied with Descartes’ explanation of the connection between body and soul, Malebranche formulated a new doctrine: occasionalism. This argues that there is no communication between the two substances; we can only speak of God’s intervention. We are not the cause of our bodily actions; God causes the desired changes in the material substance. Only God has the power to act.
Spinoza (Pantheistic Monism)
Spinoza applies the deductive method of geometry to discover the truth. He posits that there is only one substance, not three. Thought and matter exist as God’s work; therefore, only God corresponds to the idea of substance. God is infinite and contains infinitely many attributes. We know two of these attributes: thought and extension, as they are the only ones in which we participate.
Spinoza distinguishes between natura naturans (nature that is creating, God) and natura naturata (nature that is created).