Step 1: Contextual Foundation.
René Descartes, a pivotal figure in modern philosophy, posited the significance of substance and extension. His assertion that "the existence of bodies presupposes extension" signifies that physical entities must occupy space to exist. This tenet is fundamental to his materialist and dualist philosophical framework.
Step 2: Option Scrutiny.
- 1. Bacon: Francis Bacon's contributions centered on the scientific method, not on the concept of extension as emphasized by Descartes.- 2. Descartes: Correct. Descartes maintained that extension is a prerequisite for material existence.- 3. Leibniz: Leibniz's philosophy diverged, focusing on monads and metaphysical concepts rather than extension in Descartes' sense.- 4. Spinoza: Spinoza's pantheistic view identified all as a single substance, but his articulation regarding extension differed from Descartes'.
Step 3: Determination. Option 2, Descartes, is the correct identification.
Final Answer: \[ \boxed{\text{The correct answer is 2. Descartes.}} \]