Monday, March 01, 2004

There are three notes below: "The Man Born Blind"; "Plants as Doctors?"; "The Peacock's Tail: the Aftermath of an Arms Race?"

The Man Born Blind

Here is an article I published several years ago, together with some comments on Oliver Sacks' remarks on the same topic:

Seeing is Perceiving

by Julian David O'Dea

New Testament miracles of curing may be given naturalistic explanations. It may be argued that conditions were "hysterical" (all in the mind) and therefore subject to cure by suggestion. However, some New Testament cures are harder to explain along these lines [1].

Another possibility is that ordinary physical explanations can be proposed. For example, Tobias' cure of his father's blindness in the Book of Tobit could have been due to the use of a material with appropriate chemical properties to clear the cornea of the eye. Lemon juice has been used as a folk remedy for so-called "cataract", as the writer James Thurber mentioned in his correspondence [2]. Thurber had a lot of eye problems himself and was naturally interested in such matters.

If one takes the account purely at face value, Jesus' cure of "The man born blind" is not in either of the above categories. It was not "all in the mind", nor are the extraordinary and, as far as I am aware, previously unremarked perceptual aspects explicable in natural terms.

John 9, "As he passed by, he saw a man blind from his birth...We know that this is our son, and that he was born blind...Never since the world began has it been heard that any one opened the eyes of a man born blind."

This was not a case of "hysterical blindness" because the man was blind from birth. This point is made throughout the Gospel passage and his parents affirm it. It is possible that Jesus used some obscure physical cure (he "made clay of the spittle and anointed the man's eyes with the clay") to restore his sight. What remains extraordinary is the perceptual ability of the man immediately after his vision was restored.

In a classic study [3], Gregory and Wallace provided a detailed description of the aftermath of a vision-restoring operation on a man who had been effectively blind almost from birth and who, at the age of 52, recovered vision as a result of corneal grafting operations. This man had a lot of trouble using his new vision. He found that although he had vision he had little useful perception. This classic, rather sad case underscored what had been noted for some time, namely what Zangwill in his Foreword to Gregory and Wallace's book had called " the slow, laborious and imperfect way in which the perception of form is acquired by these patients [who recover their vision after early and long-standing blindness] and their liability to emotional 'crises' as they come to discover the true extent of their disability as sighted persons."

In marked contrast, there is no suggestion in the Gospel account that the man had any trouble perceiving his environment as soon as he received vision. In the case described by Gregory and Wallace the man after his operation "...did not find faces 'easy' objects. He did not look at a speaker's face, and made nothing of facial expressions." However the man in the New Testament had no problems in his dealings with the Pharisees and seemed very satisfied with his situation. There is no suggestion in the Gospel account that "The man born blind" had any trouble perceiving his environment as soon as he received vision.

Another case, more recent than the one described by Gregory and Wallace, was that of Judy Taylor, an English woman who recovered her vision as an adult thanks to a cataract operation. She had gradually lost her sight until she became blind at nine years of age. She wrote a book [4] in which she describes her experiences before and after the operation. Even though she had had vision in her childhood she still had trouble learning to see properly after her operation. She had trouble with colours and perspective and objects had to be identified by the familiar means of touch before they could be recognised visually.

So there is more to the New Testament case than meets the eye. One could argue that the man's ability to use his sight effectively as soon as he gained it was the greater miracle. The man would have had to receive not only an optical cure but also a mind trained to perceive [5].

Mark 8: 22-26: "And they came to Bethsaida. And some people brought him a blind man, and begged him to touch him. And they took the blind man by the hand, and led him out of the village; and when he had spit on his eyes and laid his hands upon him, he asked him, 'Do you see anything?' And he looked up and said, 'I see men; but they look like trees, walking.' Then again he laid his hands upon his eyes; and he looked intently and was restored, and saw everything clearly."

This case is a lot less clear cut. There is no indication of whether the man was blind from birth or early in his life, or had become blind later in life. Nonetheless the "two stage" nature of the cure is intriguing. What did the man mean when he made the puzzling remark that he saw "...men, but they look like trees, walking"? Was he trying to say that his perception was abnormal, that people looked like trees - that is did not "make sense" visually? In other words, did he mean that they looked like nondescript vertical objects? Or was it simply that they were blurred or unclear? In any case Jesus made a second follow-up attempt at a full cure, "again he laid his hands upon his eyes" and afterwards the man "saw everything clearly".

There is the intriguing possibility that this man was, like Judy Taylor, someone who became blind in early life after having had some experience with vision. Perhaps his initial perceptual problems (seeing "...men, but they look like trees, walking") were like those that Mrs Taylor experienced on regaining her vision. In the Biblical case Jesus may have been able to move on in the second part of the cure to correct the perceptual problem.

In the first miracle discussed there is no question that the cure, as described, would have had to involve a perceptual cure as well as an optical cure. My remarks on the second miracle are much more speculative, but I think worth making.

What does all this mean to a modern reader? I think it could mean a number of things depending on one's personal approach to belief. One thing is clear. The account of the miracle of "The man born blind" is an even more extraordinary story than the writer could have realised, because a writer of the time would have had no way of knowing about the impossibility of normal perception following a purely optical cure. Only modern medicine, with its cures for chronic blindness, has disclosed that.


I wish to thank the Revd Peter Mendham and Fr Keating OP for helpful discussions.


1. Leavesley, JH (1990) discusses the issue of cures of "hysterical" conditions in his Potions and Panaceas: Physicians and Prophets, Australian Broadcasting Corporation, Crows Nest, New South Wales. He also mentions cases such as the curing of congenital lameness in the New Testament which are particularly impressive because they seem to have been complete cures of genuine, chronic physical disabilities without the lingering problems one would expect and which would require (in modern terms) physiotherapy. Leavesley's book is based on a series of radio talks. There are some fascinating things in the book, including mention of a brilliant and extraordinary medical explanation for Lot's wife being turned into a "pillar of salt".

2. Thurber, H and Weeks, E, eds (1981) Selected Letters of James Thurber, Little, Brown and Company, USA, p.91.

3. Gregory, RL and Wallace, JG (1963) Recovery from Early Blindness: A Case Study, Experimental Psychology Society Monograph No.2, United Kingdom. Professor Richard Gregory is a prominent and effective writer on science. He edited the Oxford Companion to the Mind.

4. Taylor, J (1989) As I See It, Grafton Books, London. A condensed version appeared in Readers Digest of September 1990.

5. Dr John Grigg, an ophthalmologist at the Sydney Eye Hospital, advised me recently that perceptual skills must be developed during the first nine years of life while the brain is still capable of such learning ("plastic"). Functional sight cannot be achieved without this childhood experience.


Some time after I published the above in a journal called "St Mark's Review", I came across Oliver Sacks' essay "To See and Not See" in his book "An Anthropologist on Mars". Discussing cases in which sight is restored after long-term blindness, he writes "What would vision be like in such a patient? Would it be 'normal' from the moment vision was restored? That is what one might think at first. That is the commonsensical notion - that the eyes will be opened, the scales will fall from them, and (in the words of the New Testament) the blind man will 'receive' sight. But could it be that simple? Was not experience necessary to see? Did one not have to learn to see?"

Sacks also provides this footnote: "There is a hint of something stranger, more complex, in Mark's description [in the New Testament] of the miracle at Bethsaida, for here, at first, the blind man saw 'men as trees, walking', and only subsequently was his eyesight fully restored (Mark 8: 22-6)."


Plants as Doctors?

For some time, I have toyed with the idea that plants might provide substances of medical value to animals that perform useful services for them. For example, do fruiting plants provide medically useful chemicals to monkeys that eat their fruit and help spread their seeds? Could plants provide some curative products to animals that eat their foliage? That is, could a plant's leaves or fruit provide chemicals designed to help prevent or cure animals' diseases?

Certainly plants frequently secrete materials that are intended to stop animals from feeding on them; but could they do the opposite and encourage the health and survival of animals that render them services - such as spreading their seeds or fertilising them with their droppings - by providing them with useful medications?

Is it possible that some of the useful drugs that are derived from plants have their origin in keeping wild animals healthy - for the mutual benefit of the plants and animals? Is this one reason why fruit seems to be so valuable in the human diet?

There is one case that appears to show "proof-of-concept". For an account see "New Scientist" (UK) - the issue of 30 May 1998, p.27. The note is short so I'll quote it in full:

" A Beautiful Way to Keep Bees Healthy

This flower [illustrated], which is native to South and Central America, lavishes an unexpected gift on the wild trigona bees that pollinate it - a coat of resin spiked with powerful antibiotics that probably help keep their nests free of harmful bacteria.

John Loquvam of the University of Alaska in Fairbanks exposed bacteria known to infest the hives of honey bees to the resin of the flower, *Clusia grandiflora*. The resin was almost as effective at killing the bacteria as conventional antibiotics. 'It's the first time this has been shown in any plant as a pollinator reward', says Loquvam.

Resin from the female plants was far more potent than extracts from male plants. Loquvam suspects the females are compensating for the fact that males produce 15 times as many flowers. "

It seems likely that this principle - of plants providing useful animals with medicinal rewards - will be found to apply in other cases as well. It would certainly be in the interests of plants to ensure that useful animals remain free from illness and able to continue to serve the plants' purposes.


The Peacock's Tail: the Aftermath of an Arms Race?

JD O'Dea, Canberra, Australia

Petrie et al. (1991) provided evidence of a correlation between the number of eye-spots (ocelli) a peacock has on his tail and his mating success.

Manning and Hartley (1991) referred to these data and suggested that females are assessing symmetry, which they indicate is related to number of ocelli, rather than "counting ocelli" for example.

I wish to suggest that the data of Petrie et al. (1991) are most readily interpreted along the lines that female birds are stimulated by viewing eye-spots on the male's train, and that once sufficient of this visual stimulus has been continually available the female is ready to mate. Normally, this will be with a male which is effective at providing eye-spots to the female's visual field: that is, a male bird which has an array of ocelli over as large an area of her visual field as possible. A bigger train (with more ocelli) will cover more of her visual field and is more likely to maintain the stimulus of an eye-spot wherever the focus of her visual attention may wander.

Perhaps there is no need to invoke Zahavi-type hypotheses of indications of fitness, which have been advanced at times to explain the evolution of the peacock's huge tail (eg. Diamond, 1990). Simple competition among males to increase the size of the tail to maximise the effect of the eye-spot stimulus by covering as much as possible of the female's angle of vision may be sufficient explanation.

As Ridley (1981) notes, the eye, or an imitation eye, seems to be important as a behavioural releaser in a range of animals. The same author suggests that the train of the peacock serves merely as a vehicle for the ocelli, and that the effect of female preference is achieved through the form of stimulation or "hypnosis" exerted by the most perfect array of "eyes" on the expanded fan. The "eyes", he suggests, are carefully "designed" to have the maximum psychological effect on the peahen. Ridley (1981) refers to the power of the peacock's train lying in its supernormal mimicry of the obsessive fascination of real eyes.

Enquist and Arak (1993) have considered the concept that perceptual bias may play a role in sexual selection with resultant signal exaggeration.

I am suggesting here that the data of Petrie et al. (1991), the possibility of signal exaggeration (Enquist and Arak, 1993), and a variant of the ideas of Ridley (1981) may be getting us closer to a simple hypothesis to explain the evolution of the peacock's tail. This simple hypothesis does not require the peahen to count eye-spots, assess symmetry or be "hypnotised" by appreciation of a complex pattern (cf. Ridley, 1981) but merely to respond to her experience of a single releaser, the eye-spot.

In summary, the present suggestion is that the peahen is stimulated by the supernormal stimulus provided by the presentation of "eyes" in a large part of her visual field giving her a persistent form of stimulation. Male birds with the most coverage of the visual field (the largest trains with the most spots) will be the most sexually successful.


Diamond, J. 1990. Kung Fu kerosene drinking. Natural History, (7), 20-24.

Enquist, M., and Arak, A. (1993) Selection of exaggerated male traits by female aesthetic senses. Nature 361:446-448.

Manning, J.T. & Hartley, M.A. 1991. Symmetry and ornamentation are correlated in the peacock's train. Anim. Behav., 42, 1020-1021.

Petrie, M., Halliday, T.R. & Sanders, C. 1991. Peahens prefer peacocks with elaborate trains. Anim. Behav., 41, 323-331.

Ridley, M. 1981. How the peacock got his tail. New. Sci., 91, (1266), 398-401.


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