WHAT, THEN, DEFINES ART?

as said before, the purpose of a work of Art - any work of Art - is to show, to present to the world what the artist considers of fundamental importance... but if the work is to be of any worth for contemplation, it must reflect VALUES... Rand defined a value as 'what you act to gain and/or keep'... in order for a person to be able to figure out which values are best desired - and why [that is, to be able to cognitively justify them], there is this need of having an all-inclusive view of existance... furthermore, there is a need to be able to figure out which of these world viewpoints is correct - because a value, to be of any usefulness, must reflect reality, not fantasy...

but this all-inclusive view is so vast that no person could possibly be able to hold it within conscious awareness... there is just too much of it - way too much of it - for the conscious mind... yet, in order to provide yourself with a groundbase for placing your values by which you guide yourself, for INTEGRATING these specifics into the sum and whole, it is essential that you have SOME means of being able to bring this all-inclusiveness to your conscious attention...
that is what Art is all about - and THAT is the nature and true importance in being an artist... it is also what allows for a complete definition of Art, an objective, all-inclusive definition based on the nature of a human being:

Art is a selective re-presentation by the artist of aspects of reality according to how the artist fundamentally views reality...

this is why it is important to have a correct view of reality, of existance - the correct metaphysics [which is simply the term used for studying the fundamental nature of reality]... to do less is to be doing a grave dis-service to yourself as an artist, and to your viewers who seek from you examples of affirming their sense of life... as Rand pointed out, Art takes the abstractions of metaphysics and makes them into specifics, the concretes - presenting them as images... in other words, it brings the immense concept of metaphysics to the perceptual level of your consciousness, allowing you [and the viewer] to comprehend them AS IF THEY THEMSELVES WERE PERCEPTS... a faulty view of existance, therefore, a faulty metaphysics, would bring forth false images of viewing the world - including the notion that images are not needed at all...