H. Weyl stands prominent amongst other idealist scientists. We have already seen his philosophical views, which he has put forth in his chiefly scientific treatise Space-Time-Matter.[1] Weyl has clearly accepted the existence of a psychical reality (consciousness) as distinct from body or the external world. This concept of Weyl is much akin to the Jain concept of soul.
But as regards the world of our perception, his view seems to differ from the Jain view. As far as the objective existence of the external world is concerned, he seems to accept it, as he writes: "I do not, by this, in any way wish to imply that the view that the events of the world are a mere play of the consciousness produced by the ego, contains a higher degree of truth than naive realism; on the contrary, we are only concerned in seeing clearly that the datum of consciousness is the starting point at which we must place ourselves if we all are to understand the absolute meaning as well as the right to the supposition of reality."[2] Nevertheless, he denies that the world of our perception is independent of consciousness. For he observes: "A philosophic examination of the thesis of truth must and will lead to the conclusion that none of those acts of perception, memory etc. which present experiences from which I seize reality, gives us a conclusive right to ascribe to the perceived object an existence and a constitution as perceived."[3]
Further, he concludes, "In this interpretation, things of the real world are approximate ideas. From this arises the empirical character of all our knowledge of reality."[4] At another place he goes to the extent of saying that the idea of the existence of substance has, however, been finally quashed.[5] Also, as we have already seen, he considers the sensory qualities (like colour etc.) to have only a subjective existence.
Thus, conclusively we may say that according to Weyl, the external world exists objectively but the world of our perception may not be the same as the objective world and the sensory qualities in our perception are wholly subjective. Thus Weyl's view is very much identical to Eddington's 'selective subjectivism' and as we have already compared it with the Jain view, we need not unfurl the whole issue here.
Sir James Jeans is another physicist who advocated idealism as a philosophy of science. In the first chapter we have seen how Jeans considers the universe to consist of pure thoughts. But, alike Eddington, Jeans’s view is also abstruse and vague. At many places in his work (viz., The Mysterious Universe), we find him making ambiguous and even self-contradictory statements.
It is important to note the following statement of Weyl: "Philosophy, mathematics, and physics have each a share in the problems presented here. We shall, however, be concerned above all with the mathematical and physical aspect of these questions. I shall only touch lightly on the philosophical implications for the simple reason that in this direction nothing final has yet been reached, and that for my own part I am not in a position to give such answers to the epistemological questions involved as my conscience would allow me to upheld." (Space-Time-Matter, p. 2).