Everyone, if they live past a certain age (say, 10), has skeletons in their closet. Behind the closet door lurk things that don’t fit our preferred views of self and world, that we would like to keep out of sight forever – even from ourselves. This is also true of institutions, and entire cultures. All have secrets.

Since the Scientific Revolution of the 1500s and 1600s we have relied on scientists to judge the nature of reality, and to escort unseemly knowledge-claims off the premises. Let us be clear: modern science is not just another belief-system, a church among churches. It is a unique alloy of logic and observation that permits us to screen the possible against the actual. But let us also be clear about this: science, no matter how complex or sublime, is always conducted by apes. Researchers are primates too - instinctive beasts with biases of thinking and seeing that evolved over millennia on the African savannah. In the past few centuries the naked apes of science have tucked their share of bones in the closet, often for apish reasons. And those bones are restless.

The company in science’s closet has been grand. Mind, Soul, Spirit, Consciousness, God – they have all done time there among the cobwebs and unpaired mittens. But the first notion to be closeted by science is scarcely known today, though its pedigree is primal. Sages of old dubbed it Imaginatio Vera – "True Imagining". People since the Stone Age have felt that the mind’s eye can peer past the mind’s navel, beyond mere introspection, into the heart of Truth or the spirit realm. Sometimes fantasy turns out to be revelation.

One of the "True Imaginers" was Paracelsus, a Swiss doctor of the early 1500s. The medical knowledge of his age was largely worthless, he believed (and today’s scholars concur). To vex his detractors he would make public bonfires of medical texts. Turn away from the writings of fusty figures like Aristotle, he would exhort, and read the Book of Nature, using all your senses! This shift toward empiricism marks Paracelsus as the first major character of the Scientific Revolution. But Paracelsus included among "the senses" an interior organ – Imagination. He taught that the essence of each thing in the cosmos lies hidden inside us; through visionary meditation we can discover Nature’s workings from within. For Paracelsus, science was an inner and an outer exploration. He died at 48, likely poisoned by colleagues outraged at his bonfires and jealous of his healing prowess.

Another notable proto-scientist was Giordano Bruno, born a few years after Paracelsus’ demise. This Italian genius was among the first to champion Copernicus’ wonky idea that the earth and planets orbit the sun. But Bruno saw much deeper than Copernicus did. Past the orbit of Saturn, the Copernican solar system was enclosed in a gigantic beach ball with stars painted on the inside. Beyond that globe were the angels and the Lord. Bruno punctured the ball. The stars are suns, he proclaimed, infinite lights in infinite space. Many of those alien suns are ringed by planets; and some of those planets teem with life! How did a man in the sixteenth century, without rocket or telescope, glimpse the universe known to the twenty-first? Via Imaginatio Vera. But Bruno left no room for God (for the record, he said God is everywhere). Bad move. Damned for heresy, he was roasted at the stake by the Holy Inquisition.

In the 1600s the Scientific Revolution entered its adolescence and had an identity crisis. Teen apes like to see themselves as everything their parents are not; so mainstream scientists insisted they owed nothing to the wisdom traditions (aka "superstitions") that had gone before. Alchemy and Magic, science’s hoary ancestors, deployed True Imagining to plumb the mysteries. Therefore science apologists of this era would have none of it. Francis Bacon was the first writer to define scientific inquiry. He equated imagination with grime on the mirror of the mind. A scientist’s awareness should be spotless to reflect accurately the objects under study. The things of imagining aren’t objects at all, but figments. Imaginatio Vera, get thee to a closet.

For three hundred years Bacon’s exorcism held – science was officially objective, not imaginative. By the mid-twentieth century, scientific psychology had embraced Behaviourism, declaring consciousness (including imagination) impossible to measure and thus irrelevant. Human beings were reduced to nervous systems linking itches and twitches (in Psych 100-speak, "stimuli" and "responses"). No soul, no mind, no imagination required. Then came the drugs.

In 1947 the first scientific article on the effects of LSD was published. Aldous Huxley’s The Doors of Perception, in which he recounts his mescaline trips, came out in 1954. Two years later the word "psychedelic" was coined. Then Life magazine did a piece on Mexico’s magic mushrooms. By the early ‘60s, consciousness-expansion had become a cultural force in North America. From the psychedelic angle the mind seemed much vaster and more multidimensional than the rats-and-mazes set had let on.

Among those at the forefront of the psychedelic movement were scientists, including a trio of psychologists – Timothy Leary, Richard Alpert (later renamed Ram Dass) and Ralph Metzner (editor of Psychedelic Review, which began publishing in 1963). These mavericks were given the bum’s-rush from academia. But it was too late. The closet door was ajar. Robert Holt’s landmark article featured in a 1964 issue of American Psychologist. Entitled "Imagery: The return of the ostracized", it welcomed the imagination back as a proper topic for research. Since then, thousands of studies have been done on the roles imagining plays in memory, perception, problem-solving and mental illness. Imagination now seems implicated in every sphere of life.

And what of Imaginatio Vera? Could it too regain a role in the scientific vision? The greatest scientists always doubted the dualism of Science and Imagination. Take the undisputed titans of physics – Newton and Einstein. Newton founded modern physics as a sideline. His passion was Alchemy, the mystical probing of matter with True Imagining. Einstein noticed that physics is based on mathematics, and that mathematics is in fact a species of imagination. The eyes of flesh have never viewed a perfect triangle, or the number nine. These things are imaginary. Yet the success of mathematical science proves that such "figments" are cryptically entwined with the roots of reality. Einstein, with no inquisitors over his shoulder, wrote that "Imagination is more important than knowledge". It now seems plain that in their monkey-zeal to be special, seventeenth-century scientists hid their own identity from themselves: modern science is not the opposite of True Imagining, but its triumph.