Locke & Hume’s Ideas, Descartes’s Substance & God

Locke: Definition and Types of Ideas

When Locke speaks of “Idea”, he understands “everything we know or perceive.”

Simple Ideas

These are ideas that cannot be broken down into others, necessarily imposing themselves on the mind, to which it remains passive.

a) Ideas of Sensation

These come from external experience: impressions produced on our senses by external objects in the outside world. Through them, we capture the qualities of bodies, which may be of two types:

  • Primary Qualities: These are objective and inherent to objects, such as size and shape.
  • Secondary Qualities: These are subjective, such as smell, taste, and color.

b) Ideas of Reflection

These come from inner experience: the knowledge that the human mind has of its own actions, such as thinking, doubting, and perceiving.

c) Mixed Ideas

These originate from combined data of sensation and reflection.

Complex Ideas

These are ideas produced by the human mind from simple ideas, where the understanding is now active. They can be of three kinds:

  • Modes: These are formed by combining simple ideas and refer to no remaining properties.
  • Relationships: These are formed by comparing one thing with another.
  • General or Universal Ideas: These are formed by abstraction. The idea of substance is one of them.

Hume: Impressions and Ideas

Hume proposes a different classification from Locke. He calls all acts and mental contents “perceptions” and distinguishes two kinds: impressions and ideas.

An impression is the current perception, immediately captured by the senses, while ideas are representations or copies of the impressions left in the mind. Impressions have more vivacity and intensity than ideas.

Impressions, in turn, can be of sensation (from the external senses) and reflection (from the interior of our consciousness).

Both impressions and ideas can be simple or complex. In the first case, they do not accept any distinction or separation. As for the complex, they are formed by the grouping of simple perceptions and can be divided into parts.

“It is necessary that the simple ideas are associated according to laws of association”: resemblance, contiguity in time and space, and cause-and-effect.

Descartes: God, Substance, and the World

The Subject of God

For Descartes, “subject” means any content or idea of conscience. He identifies three classes:

  • Adventitious: From outer reality.
  • Factitious: Created by the imagination from other ideas.
  • Innate: These are in our mind before any experience or perception. Innate ideas are the foundation from which our knowledge is built. For example, the idea of infinity cannot proceed from finite beings, since all things are finite. Neither can it come from our own thinking, as we are finite beings and our thinking is flawed and assaulted by doubt. The idea of infinity can only have arisen in our minds by the action of an infinite being, God.

Descartes uses the Ontological Argument of St. Anselm to prove the existence of God: from the idea of an infinitely perfect God, His real existence is demonstrated. “God is the foundation of certainty, God is infinitely good, He cannot let me be fooled when I see something as obvious. God guarantees that what I perceive clearly and distinctly is true.” This is a circular argument: it relies on the criterion of certainty to prove the existence of God, who in turn guarantees that the criterion of certainty is valid.

The Structure of Reality: The Three Substances

“Substance” means “that which exists in such a way that it does not need another thing to exist.” There is only one true substance: God, the infinite substance (res infinita).

In humans, there is a substantial duality: we are formed by the soul, the thinking substance (res cogitans), and the body, the extended substance (res extensa). There is interaction between them. To explain this communication, Descartes proposes the pineal gland as a point of connection between consciousness and matter.

Descartes’s solution to the body-soul interaction problem is considered poor and unconvincing: how can a physical process affect the mind, and how can a mental process cause changes in a material object? The relationship between substances, between thinking substance and extended substance, is one of the most complex problems posed by rationalism.

SUBSTANCESATTRIBUTESMODES
SOULRes cogitans (thinking substance)ThoughtConcepts, judgments, feelings, emotions, decisions…
WORLDRes extensa (extended substance)ExtensionShape, position, movement…
GODRes infinita (infinite substance)InfinitudeGoodness, wisdom, justice…

The Mechanistic Extended Substance

Descartes proposes a purely mechanistic interpretation of the physical world. The universe can be explained by only two principles: matter and motion. The cosmos is a giant mechanism in constant motion, governed by immutable laws that can predict its course. Bodies move mechanically, without a final cause.

“God created the first matter and endowed it with a certain amount of movement. The material itself is inert.” Descartes eliminates any idea of momentum or energy; the universe operates according to two principles: the principle of conservation of matter (the amount of matter remains constant) and the principle of inertia (a body remains at rest or in motion unless other forces act upon it).

Descartes does not accept the existence of a vacuum. Matter is infinitely divisible extension without limits, circulating in many forms. This explains the plurality of bodies and the diversity of changes that occur in nature.

Descartes is only interested in the primary qualities of bodies, those that can be expressed mathematically, measured, or quantified; these are objective. Secondary qualities are subjective: individual reactions to the stimuli that are perceived.

“The universe is a great machine, whose operation is expressed in mathematical laws. The actions and movements of bodies can be translated into algebraic equations.” Descartes is the creator of analytic geometry, dispensing with any sensible representation to explain the universe and doing so only through algebraic formulas, which are located exclusively in the realm of pure reason.

The mechanistic view also applies to animals and plants. To explain the operation of organic bodies, it is not necessary to admit the existence of a soul; mechanical forces are sufficient. Even the human body itself is a pure mechanism. Living beings are seen as mere automatons: they lack sensitivity, emotions, and, of course, ideas, which are aspects exclusive to human beings.