Imagination
What is it?
It seems to be a faculty that enables us to create mental scenarios or models of reality, especially as projections of what might take place in an imaginary future - a sort of mental time travel. Or it enables us to abstract from actual situations and arrange a version of reality in our heads. Saying that, we could almost declare that all of our mental perception is imagination since it is modified in various ways by each person according to their own mental apparatus, their capacities, life experiences and how these in turn have conditioned us to perceive reality in certain ways.
Why do we need it?
To me it seems to have developed as a means for survival and helps account for our success as a species. This ability to abstract important features from reality; to investigate possible outcomes mentally, find and weigh up better strategies and then reapply them cooperatively to our actual situation - not only that, but to re-iteratively remember and record the result not only greatly enhances our survival chances - it improves our quality of life exponentially above that of other species on this planet.
What can go wrong when we use it? Does it need to be disciplined, tamed, by reason and logic?