Observations placeholder

As described in Illustrations Of The Influence Of The Mind Upon The Body In Health And Disease, Designed To Elucidate The Action Of The Imagination - Daniel Hack Tuke, M.D., M.R.C.P.,

PART I. THE INTELLECT.
CHAPTER II. INFLUENCE OF THE INTELLECT ON SENSATION.

Sir Isaac Newton in a letter to Locke (King's Life of Locke. 2 vols. 1830, I, p. 40), describes how he once looked a short time at the sun in a mirror, and then turned his eyes into a dark corner of his room till the spectrum vanished, repeating the experiment three times. The third time he found to his amazement, when the light and colours were almost gone, that they began to return "by intending his fancy upon them," and became as vivid as when he had just looked at the sun, but if he ceased to intend his fancy upon them, they vanished again.

"After this," he says, "I found that as often as I went into the dark and intended my mind upon them, as when a man looks earnestly to see anything which is difficult to be seen, I could make the phantasm return without looking any more upon the sun, and the oftener I made it return, the more easily I could make it return again."

At last he brought his eyes "to such a pass" that he had to shut himself up in a dark room for three days together " to divert my Imagination from the sun ; for if I thought upon him, I presently saw his picture, though I was in the dark." By this method, and employing his mind about other things, he began in a few days to have some use of his eyes again. Yet for some months after, "the spectrum of the sun began to return as often as I began to meditate upon the phenomena, even though I lay in bed at midnight, with my curtains drawn."

When Newton wrote this interesting account to Locke, he said he had been several years very well, but he thought that he could recall the spectrum "by the power of his Fancy," if he durst try. He adds, that such an occurrence involves a question "about the power of Fancy," which he confesses is " too hard a knot for me to untie," but inclines to refer it to "a disposition of the sensorium to move the Imagination strongly, and to be easily moved, both by the Imagination and by the light, as often as bright objects were looked upon."

Another remarkable observation was made by Newton in this case. He had only looked at the sun (in the mirror) with his right eye, yet he found that "my Fancy began to make an impression on my left eye as well as upon my right," and he could see the spectrum of the sun if he did but intend his Fancy a little while upon it. So that here the powerful direction of Thought or Attention produced the same effect on the left eye, or a point in the optic ganglia corresponding thereto, as that of the sun itself upon the right eye.