Putnam is a philosopher deservedly famous for 1. writing in a very ambigous
and confusing style; 2. making a big deal of small issues and 3. changing his
mind very often. Such is the case with the first part of this book, whereis
Putnam simply tells us that he thought it over and now believes our perceptions
tells us the truth. He used to side with most philosophers who think
perceptions are "intermediaries" between our mind and reality. We'll never
truly know what is out there. Now Putnam believes we do know what is out
there: it is what we perceive.
The second part of the book is occupied with the mind-body problem.
Putnam takes issues against two popular views. First, he criticizes the thought
experiment of the "zombie", a being who is identical to you atom by atom
but does not have a mental life. Putnam thinks this is an oxymoron because
mental life is caused by your bodily content. Therefore, same body same mind.
On the other hand, Putnam also takes issue with the "identity theory" that
mental states are identical with physical states of the brain (the same way
electricity is identical with the motion of charged particles).
Putnam thinks that mental states are, in a sense, outside the body.
To some extent, mental states are due to the environment. The content of a
mental state depends the environment and may vary between identical people in
different worlds. For example, the concept of water that I have depends on
the fact that I grew up in a world where water is what it is in this world
and it has been named that way, and used for some purposes and so forth.
In another world, my concept of water would be different.
Putnam prefers to think of the mind as a set of skills, or capacities.
All of this is fine and dandy but: 1. it is not written in a very clear
style, so it lends itself to several possible interpretations;
2. it makes a big deal of a couple of trivial ideas that are shared by
billions of people who did not spend the best years of their lives pondering
and 3. we already know that Putnam will change his mind again
(long may he live, of course).
See also MIND, LANGUAGE AND REALITY (1975)
REASON, TRUTH AND HISTORY (1981)
REPRESENTATION AND REALITY (1988)