Rachel asked:

How do our conceptions of meaning, truth and knowledge relate us to the external world? What does
'external world' mean?

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Most of humanity, including some philosophers, postulate from their everyday experiences the
existence of an 'external world'. Most people, excluding some philosophers called 'Idealists', and
some called 'Rationalists', believe that all experience is generated in a solid (material) world, and fed
to our brain (mind) by way of the five senses. Philosophers who claim that all knowledge comes to us
through the senses are called 'Empiricists'. Some empiricists claim that our senses interpret an
external material world as it really is, a tree is a tree, a house is a house, a stone is a stone, etc.: we
simply see, hear, feel, taste and scent 'what there is', the only mental link is language, by which we
make our identifications and exercise our communication skills. Most of those who believe in an
external material world are also 'reductionists', any material object reduces down to smaller material
objects, descending finally to atomic particles.

Those who hold the belief that there is an external world which coincides directly with what we could
call the popular or naive notion of reality, hold that this world is controlled by physical laws, which
humans ignore or defy at their peril. The mind, though important, has a limited input within the bounds
of natural law. On the other hand, those who are called idealists and rationalists believe that the mind
plays the major role in establishing reality in the world. There are though some very intricate
complexities and some distinctive variations within the metaphysics of both idealism and rationalism
which cannot be entered into here. Suffice it to say for the purpose of answering your question that
within this complexity is a general notion that there can be no real proof available of an external
world, because we do not have direct access to such a world; all we do have access to are our own
mental interpretations of what is given to us by our senses.

You may now appreciate that meaning, truth and knowledge are very much dependent on your world
view. With regard to truth, the general view for those believing in an external world, is that for a
proposition to be true it must correspond to a fact in the world. When we are concerned with
observing the external world, we talk about 'perceiving' things, in other words the information coming
to us by way of our senses are 'percepts'. To build up an understanding of the external world we are
obliged to bring to bear mental processes on these percepts to form what we call 'concepts'. Without
going too deeply into the ramifications of concept formation, I shall say that contained in what is
referred to as knowledge of the world is the formation and association of concepts.

Meaning, truth and knowledge are, therefore, embodied within the concepts which constitute our
world view. Because the senses cannot always be trusted we sometimes form false or mistaken
concepts; meaning, truth and knowledge can be distorted by false percepts leading to errors in our
understanding, such errors often lead to conflict between individuals and even nations. Also some
concepts can mean different things to different people, and when reflected back into the world will
lead to different views of the same subject or event. This leads us back into reflections on truth and
reality. Is there a fundamental truth, and what do we mean by reality? Questions that will probably
fascinate philosophers for many years yet.

John Brandon