Week 3: Mechanisms in Biology

Aims of Science and Philosophy

What is science for? Possible answers: truth, explanation, prediction, human welfare, power.

What is philosophy for? Possible answers include the same, plus edification, consolation.

Anti-realism in science: Science aims to make successful predictions of observed phenomena.

Realism: Science aims, and sometimes succeeds, to achieve theories that provide explanations and approximate to truth.

According to realists, inference to the best explanation justifies adoption of theories a tentatively true, but anti-realists reject this kind of reasoning. This is one of the ways in which epistemology and metaphysics interact.

What is explanation?

Deductive-nomological: An explanation is a deductive argument in which the premises include general laws and what is to be explained is a statment that follows from the premises.

Statistical: An explanation describes the factors statistically relevant to the occurrence of an event.

Schematic: An explanation fits something to be explained into an organized pattern or schema.

Linguistic/pragmatic: An explanation is an answer to a question.

Analogical: An explanation compares something to be explained with something similar that is already understood.

Causal: An explanation shows how something fits into the causal structure of the world.

Mechanism: An explanation of something describes the causal mechanism that produces it.

What is a mechanism?

The ancient Greeks were familiar with simple machines, such as levers, screws, wheels. Epicurus and other materialists originated the explanation of nature in terms of mechanisms.

Mechanism was revived in the 17th century: Descartes, Hobbes, Newton, etc. By this time, much more complex mechanisms were known, e.g. clocks. Today we have much more complex mechanisms to use as models, e.g. computers.

Discussions of mechanisms are ubiquitous in modern molecular biology, medicine, and cognitive neuroscience, but philosophers have only recently paid attention to mechanistic explanations.

Machamer, Darden, and Craver (2000, p. 3) characterize mechanisms as “entities and activities organized such that they are productive of regular changes from start or set-up to finish or termination conditions”.

Bechtel: mechanisms are systems of interrelated parts that interact to produce functional behaviors.

Schema for a mechanistic explanation:

Explanation target:

Why does a system display a particular behavior?

Explanatory pattern:

The system consists of interrelated parts (entities).

The parts interact via their behaviors (activities).

The interactions of the parts in the system cause the behavior.


Bicycles move because they have parts such as wheels, pedals, and chains that interact to make them move.

Discussion Questions for Week 4

  1. How do ethical questions about life and death depend on metaphysical and epistemological issues?
  2. What are the implications of a mechanistic theory of life for issues such as euthanasia, brain death, and abortion?
  3. What does the nature of life tell us about the nature of death?
  4. What do different conceptions of life suggest about the nature of a person?
  5. When is a person with severe brain damage no longer alive?
  6. Would you want to survive death by having your brain downloaded into a computer?
  7. What does the nature of life and death tell us about the morality of euthanasia?


Life, Mind, and Disease

Computational Epistemology Laboratory.

Paul Thagard

This page updated Sept. 27, 2004