Plato's Forms
One book I am reading, relevant to the idea of imagination and Plato's idea of forms is, 'The Physics of Transfigured Light: The Imaginal Realm and the Hermetic Foundation of Science', by Leon Marvell (2016). In this book, the author is exploring the whole dimension of ideas.
In it he says,'a disciplined imagination leads one to a more accurate picture of reality, and an unfettered imagination leads one more astray.' I think that this distinction is important because we are looking at the difference between seeing subjective truths and more objective ones, although I am not sure that this distinction is clearcut.
He also suggests a,
'notion of ideal objects existing in fourth-dimensional space. Rather than a world of physical objects, however, it is a "problem space. Of central importance is the notion that ideas and conceptions possess a logical dimension outside of time, such that the force of certain ideas will become apparent to certain individuals outside of material, causal factors.'
I am aware that this quote does refer to it as a 'logical dimension', but nevertheless it is one which involves the imagination in order to enter into it. This is the way I see imagination, as not just being about mere personal fantasy, but of connecting to a dimension in its own right, and I believe that belief in Plato's idea of forms is dependent on this. So, the way in which imagination is involved is as a means of tapping into this source. It is a way of knowing which does involve reason and logic, but the point which I would stress is that it does suggest a realm or objective dimension, and this also involves imagination in the true sense of the word, as in conjuring up images.