PHIL 255: Philosophy of Mind, Week 5


Thursday, Oct. 13: Class will be held in ES1 132.

Thursday, Oct. 27: The exam will be written in other classrooms: watch for announcements.


5a, Mind & Brain, continued


Explaining depression: why?

1. Depleted biogenic amines? Low serotonin? Prozac.

2. Inhabited by evil spirit?

3. Bad family relations?

4. Thwarted career?

Intentionality in depression

People get depressed about something.

Note effectiveness of cognitive therapy, in combination with Prozac.


supervenience - A set of properties or facts M supervenes on a set of properties or facts P if and only if there can be no changes or differences in M without there being changes or differences in P.

For every psychological difference, there has to be a neurophysiological difference. If 2 people have the same brain facts, then they have the same mind facts.

Identity implies supervenience, but not vice versa.

Multiple instantiation: mind could be in many different kinds of matter, e.g. Martians, computers.

But this is just a thought experiment: minds like ours may in fact depend on having brains and bodies and environments like ours.

Explanation of behavior

Does brain suffice to explain mind?

- need mind facts and social facts to explain depression

- e.g. low serotonin + stress + trauma -> severe depression.

But this does not undercut materialism, since the other causal factors are material too.

Conclusion: The explanation thesis may be problematic because no complete reductive explanation may be achievable (the mind/brain is too complex).

But the identity and exclusion theses may be upheld, if intentionality can be understood materially.

5b, Persons

Thought experiments: personhood

Gender: Le Guin's kemmer - becoming a different sex

Loss of mind

Loss of body, e.g. Christopher Reeves

Aspects of personhood

Memory: autobiography, e.g. remembering childhood

Conviction of freedom: deliberation and decision

Free will

But is freedom of action just an illusion?

Dualism: we have free will because we have a non-material soul, not subject to physical causality.

Materialism: since mind is matter, and changes in matter are caused, there is no full-fledged free will. What you do is the result of electrochemical processes in your brain.

But some materialists are compatibilists, claiming that causality and freedom can co-exist: you are free when you could have done otherwise if you had chosen.

Free will is an illusion, but freedom isn't. You are free when the causality is internal, based on your own beliefs and desires, rather than external coercion.

What is the function of regret and blame?

Folk psychology: everyday explanations of behavior in terms of beliefs, desires, and emotions.

Eliminativist materialism: we don't need to reduce folk psychology to neuroscience, because folk psychology is mostly false can be rejected.

Happiness and depression

Why are some people prone to depression, while others are chronically cheerul? Possible explanations:

Is happiness a brain state?

Graham: self-respect is a crucial part of ongoing happiness.

William James: self-esteem = successes / pretensions.

Keith Oatley: happiness comes from satisfying goals.

Phil 255

Computational Epistemology Laboratory.

Paul Thagard

This page updated October 7, 2005