Descartes and Bentham

Ideas of Early Modern Philosophers

Rene Descartes (1596?1650, French philosopher)

Theory of Animals as Machines
(Discourse on the Method, 1637)

Machines such as clocks move regularly through the combination of their parts. Likewise, animals behave mechanically through the combination of parts given by nature.

Animals are "mere machines" because they do not possess minds (souls).

Humans are not "mere machines" because they possess minds.

The proof that only humans possess minds (reason) is that only humans can speak language.

Therefore, humans are able to use animals as tools.

Mechanical view of the world ? the belief that everything in the world operates according to physical laws.

Reductionism ? the idea that even complex phenomena can be understood completely by breaking them down into their individual components and understanding those parts separately.

However, while the human "body" can be explained through reductionism, the human "mind" cannot.

Mind?body dualism ? the belief that human beings consist of two different entities: the "body" (including emotions), which is material, and the immaterial "mind."

Here, "mind" refers to higher human mental functions such as thought, consciousness, and language, which only humans possess. Emotions, which animals also possess, are not included in this concept of "mind."

Animal spirits ? Descartes believed that psychological phenomena such as emotions (passions) could be explained physiologically by a substance called "animal spirits" (something like a type of blood).

Cogito, ergo sum ? "I think, therefore I am." Even if one doubts everything, one cannot doubt the existence of oneself as a thinking being. That alone is certain. Everything begins from one's own thinking. (Discourse on the Method)

Immanuel Kant (1724-1804, German philosopher)

Teleology

Animals do not possess self-consciousness.

Animals exist merely as means to an end.

That end is human beings.

Therefore, humans are able to use animals as tools.

Jeremy Bentham (1748-1832, British philosopher)

Utilitarianism
("The greatest happiness of the greatest number")

A morally right action is one that brings as much happiness as possible into the world.

Pain is the greatest enemy of morality.

If we wish to be moral, we must not inflict pain on beings that can feel pain.

Animals also have sensations and can feel suffering; therefore, they deserve to be treated morally.

Therefore, their rights must be protected by law.