Aristotle, who has been credited with inventing the concept of imagination, used the Greek word “phantasma” (a term used by Plato to refer to reflections in mirrors or pools) to mean "[mental] image".
Aristotle describes phantasmata as being analogous to paintings or wax impressions (De Memoria 450a-b), and as “a residue of the actual [sense] impression” or “a movement resulting from an actual exercise of a power of senses". He believed linguistic meaning derived from imagery, spoken words as the symbols of our inner images.
From a non-philosophic point of view, Descartes believed the pineal gland in the center of the brain was somehow able directly to affect, and be affected by, the thoughts of the immaterial soul, as a result of the formation of optical images on the retinae of the eyes.
Notable work in this area was also done by Kant, Hobbes and Locke.
Let's skip ahead to to the 20th century. A group of psychologists working in Würzburg, Germany, come up with the imageless thought theory and cause a huge controversy that is never completely resolved.
The Würzburg group believed that thought should be understood in terms of language per se, and that it was a serious mistake ever to have believed that the representational power of language derives from some more fundamental form of representation, such as mental imagery.
In the 60's, Canadian psychologist Allan Paivio quietly worked on proving his Dual Coding (imagery code and verbal code) theory of the imagination.
He demonstrated quite incontrovertibly that subjects who follow explicit instructions to use simple imagery-based mnemonic techniques to memorize verbal material (typically lists of apparently random words, or word pairs) remember it very much better than subjects who do not use such technique.
Secondly, and somewhat more controversially, Paivio and others claim to have shown that imagery plays a large role in verbal memory even when the experimental subjects are not given explicit instructions to form imagery, and make no deliberate effort to do so.
More recent work has sought to explore the relationship between current conceptions of mental imagery and the more resonant, but more nebulous, notion of imagination (and related concepts such as insight and creativity) (White, 1990; Brann, 1991; Finke et al., 1992; Thomas, 1997a,b, 1999a,b, 2006; Kind, 2001; McGinn, 2004; Blain, 2006).
Perhaps the most ambitious claims in this regard are those of Arp (2005, 2008), who comes at the matter from the controversial perspective of evolutionary psychology.
Arp suggests that scenario visualization is unique to the human species, and is the crucial factor that has made our high-level creative problem-solving abilities possible. From this perspective, it is in large part thanks to our capacity to form and manipulate mental imagery that humankind has been able to out-compete rival species, and develop our complex cultures and technologies.
So whether Frank Lloyd Wright was talking about imagination as his spiritual or literal, physical salvation, he absolutely nailed it.
