Sri Aurobindo
Letters on Yoga
4. Reason, Science and Yoga
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The difficulty is that you are a non-scientist trying to impose your ideas on the most difficult because most material field of science – physics. It is only if you were a scientist yourself basing your ideas on universally acknowledged scientific facts or else your own discoveries – though even then with much difficulty – that you could get a hearing or your opinion have any weight. Otherwise you open yourself to the accusation of pronouncing in a field where you have no authority, just as the scientist himself does when he pronounces on the strength of his discoveries that there is no God. When the scientist says that “scientifically speaking, God is a hypothesis which is no longer necessary” he is talking arrant nonsense – for the existence of God is not and cannot be and never was a scientific hypothesis or problem at all, it is and always has been a spiritual or a metaphysical problem. You cannot speak scientifically about it at all either pro or con. The metaphysician or the spiritual seeker has a right to point out that it is nonsense; but if you lay down the law to the scientist in the field of science, you run the risk of having the same objection turned against you.
As to the unity of all knowledge, that is a thing in posse, not yet in esse. The mechanical method of knowledge leads to 
certain results, the higher method leads to certain others, and they at many points fundamentally disagree. How is the difference to be bridged – for each seems valid in its own field; it is a problem to be solved, but you cannot solve it in the way you propose. Least of all in the field of physics. In psychology one can say that the mechanical or physiological approach takes hold of the thing by the blind end and is the least fruitful of all – for psychology is not primarily a thing of mechanism and measure, it opens to a vast field beyond the physical instrumentalities of the body-consciousness. In biology one can get a glimpse of something beyond mechanism, because there is from the beginning a stir of consciousness progressing and organising itself more and more for self-expression. But in physics you are in the very domain of the mechanical law where process is everything and the driving consciousness has chosen to conceal itself with the greatest thoroughness – so that, “scientifically speaking”, it does not exist there. One can discover it there only by
occultism and yoga, but the methods of occult science and of yoga are not measurable or followable by the means of physical science – so the gulf remains still
in existence. It may be bridged one day, but the physicist is not likely to be the bridge-builder, so it is no use asking him to try what is beyond his province.
Current publication:
Sri Aurobindo. Letters on Yoga // SABCL.- Volume 22. (≈ 28 vol. of CWSA).- Pondicherry: Sri Aurobindo Ashram, 1971.- 502 p.
Other publications:
Sri Aurobindo. Letters on Yoga. I // CWSA.- Volume 28. (≈ 22 vol. of SABCL).- Pondicherry: Sri Aurobindo Ashram, 2012.- 590 p.
[Largest or earliest found passage: ] Sri Aurobindo. Letters of Sri Aurobindo: In 4 Series.- Forth Series [On Yoga].- Bombay: Sri Aurobindo Sircle, 1951.- 652 p.