Descartes: Methodical Doubt and the Cogito Principle

Cartesian Notions: Doubt and Certainty

With doubt begins the implementation of the method. As the first rule states: "Never accept anything as true without having met with evidence that it is so, avoiding precipitation and prejudice, and including nothing more in my judgments than what presents itself so clearly and distinctly that I have no reason to doubt it."

Defining Cartesian Methodical Doubt

Cartesian doubt is a methodical doubt. It involves provisionally considering as false those opinions, beliefs, and knowledge previously taken as true, questioning them, and treating them as false. Methodical doubt is a way or path to reach indubitable truth, unlike skepticism, which remains perpetually in doubt.

The Reasons for Doubt

The processes (reasons for doubt) include:

• Doubting the senses.
• Doubting the external world (the sleep-wake distinction).
• Doubting one's own reasoning.
• The Evil Genius Hypothesis (featured prominently in the Meditations).

The Cogito and the Criterion of Certainty

With the intuition of the Cogito, we find the criterion of certainty: clarity and distinction. All that I perceive in this way is true. The initial questioning seems to lead toward skepticism, but upon reaching "I think, therefore I am" (*Cogito, ergo sum*), we recognize this as the first principle we seek. This truth is the starting point of Cartesian philosophy.

Dissecting the First Truth (The Thinking Thing)

What am I? I am a thing that thinks, which certainly includes imagining, wanting, feeling, and refusing.

This encompasses all the activity of thought. I may doubt the existence of the objects of my thoughts, but I cannot doubt the existence of the thoughts themselves.

The activity of thinking must belong to something or substance.

Defining the Criterion of Certainty

I am sure I am a thinking thing, but what are the requirements to be certain of anything else? The rule is: Take as true only what I perceive clearly and distinctly.

We must not confuse evidence (which is not a property of ideas) with certainty (the state of mind that believes it possesses the truth). Certainty is opposed to doubt. Subjective certainty is a mental position from which I am sure.

Descartes' Classification of Ideas

According to their origin, Descartes classified ideas into three types:

• Innate: Ideas that are born within me.
• Adventitious: Ideas that appear in the human mind "as coming from outside" (e.g., tree, star).
• Factitious: Combinations created by fantasy, representing invented things (e.g., siren, Cyclops).

For Descartes, there is no possibility of a thought existing without a subject to think it. Thus, the first truth that must be affirmed is the thinking self: Cogito, ergo sum.