Rationalism vs. Empiricism: Descartes’ Dualism and Locke’s Theory of Ideas
Descartes: Existence of Material Fact
The existence of God warrants the correspondence between being and knowledge. God is perfect because He is omnipotent.
Three Areas of Reality (Substances)
Descartes established three areas of reality. One area is identified with Extended Substance (Res Extensa), which is characterized by extension and motion. That is, the world is a physical entity that occupies space.
The Mechanistic Worldview
Descartes defines the world as mechanistic (a quantity of matter with local movement in a full world). He speaks only of magnitude, so that all natural events can be measured within the great machine of the universe.
Its features are:
- Extension
- Movement
- Principle of Inertia
- Conservation of Movement
The causal influence of one body on another, and the connection between mind and body, is established by Descartes through what he called the pineal gland.
Descartes: Provisional Morality
In human behavior, morality is the ethic that helps us determine how to act. Descartes views morality as a preliminary intellectual property and a strong, Stoicist moral character.
The moral basis relies on the Sovereign Good (building understanding to choose what is presented as good). Its key feature is the basic power of the Res Cogitans (thinking substance), which includes the freedom derived from the innate idea of the self.
Moral doubt is necessary because we have a present need for happiness, which is the goal of the Provisional Morality. Its sole purpose is to justify the religious, political, and moral order.
The Three Rules of Provisional Morality
- Follow the rules, customs, and religion of the country, guided by sensible views.
- Be firm and constant in decisions, even those based on doubt.
- Be governed by reason and alter desires, rather than attempting to change the world order.
John Locke: Origin and Limits of Knowledge
Genesis of Ideas
Locke argues that innate principles or ideas do not exist. All our ideas originate from experience. The genesis of our ideas through experience constitutes the limit of our knowledge.
Types of Ideas
Simple Ideas
Simple ideas are the atoms of knowledge. Locke identifies two subclasses:
- Ideas derived from Sensation (External Experiences).
- Ideas derived from Reflection (Internal Experiences).
Locke differentiates ideas of sensation into:
- Primary Qualities: (e.g., Figure, Size, Solidity). These exist inherently in the object.
- Secondary Qualities: (e.g., Color, Smell, Taste). These are powers in the object to produce sensations in us.
In the reception of simple ideas, the human understanding is passive.
Complex Ideas
Complex ideas arise from the combination of simple ideas. In the development of complex ideas, the understanding is active, combining and relating simple ideas.
Locke identifies three classes of complex ideas:
- Substance
- Modes
- Relations
Regarding the idea of Substance, consider a rose: it presents a set of simple sensations (smells, colors, shapes, tactile sensations). According to Locke, we only perceive these qualities. We do not know what the rose is; we assume that beneath these qualities there is an unknown support (the substratum).
The idea of substance is formed in the following way:
- We link a set of simple ideas together.
- We refer to this collection with a single name.
- We conceive a general idea of Substance as the support for these sensible qualities.
- We apply this idea to all sensible things, assuming this support is necessary for the internal structure of substances.
Certainty of Existence (Self, God, and Bodies)
Locke distinguishes three degrees of certainty regarding existence:
- The Self (I): We have intuitive certainty of our existence. (Locke acknowledges the Cartesian theory here, referencing the celebrated affirmation: “I think, therefore I exist.”)
- God: We have demonstrative certainty of God’s existence. (God’s existence can be demonstrated using the argument from contingency.)
- Bodies (The World): We have sensitive certainty of the existence of bodies, witnessed by the sensations they produce in us.