Cat asked:

I've though about this question loads and I'm really confused: Is it possible that all the world just
exists in our heads?

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If all the things in the world exist in our heads, and our heads are in the world, then our heads exist in
our heads. Now that is really confusing!

I suppose what you mean is, Is it possible that all the world exists in our minds,where the existence
of a mind does not require the existence of a material object, such as a brain or a skull bone.

The first thing to point out is if I really thought it was possible that there were no material things, and
that everything 'external' I see around me is nothing more than a kind of projection of something
within my own mind, then I would seriously question whether youexist, as a separate subject with a
mind. All I know of you are words on this computer screen! But then I might go on to question whether
my wife and children exist. Everything I know of them, just as everything I know of you, is based on
experiences in my own mind. Our own experiences are all that any of us ultimately has to go on.

Having got that far, there is still more to doubt. All I know of my pastexperiences is what I can
remember of them now. So my past experiences might be nothing more than a projection of
experiences currently occurring in my mind. I could have come into existence one minute ago with all
my apparent 'memories' as they are now, and I would never know.

Even if, armed with a good dose of common sense, all these speculations seem to us highly
improbableare then still possible? Do they make logical sense? Do I have to remind myself every so
often that this wide, wonderful world and all the people in it might,just possibly, be nothing more than
a momentary bubble of experience that calls itself 'I'? A mere illusion of a 'world' which appeared out
of nowhere and will disappear the next moment into the nothingness from whence it came?

So far as nothing is absolutely certain in philosophy, I have to concede — though I don't like it — that
what I have just said is possible.

That's not the question we should be asking. The real question is whether it is possible that we might
be persuaded,by the philosophical argument of a Berkeley, or a Leibniz or a Kant, to embrace one or
other version of the theory that what we call 'the physical world' is not real in itself, but rather
something woven together out of the strands of experience.

Kant's theory is in some ways the most attractive of the three. He held that realityis something apart
from the things that appear in our experienced 'worlds'. Berkeley, Leibniz and Kant are all agreed that
there cannot be appearances without somethingbehind those appearances, their ultimate source.
Kant was the only philosopher out of the three to realize that this 'something' would have to be totally
outside all human knowledge and experience.

Geoffrey Klempner