An excerpt of Albert Einstein’s 1918 address to the Physical Society in Berlin on the occasion of Planck’s 60th birthday (the emphasis is my addition):
Nobody who has really gone deeply into the matter will deny that in practice the world of phenomena uniquely determines the theoretical system, in spite of the fact that there is no logical bridge between phenomena and their theoretical principles; this is what Leibnitz described so happily as a “pre-established harmony.” Physicists often accuse epistemologists of not paying sufficient attention to this fact. Here, it seems to me, lie the roots of the controversy carried on some years ago between Mach and Planck.1
The longing to behold this pre-established harmony is the source of the inexhaustible patience and perseverance with which Planck has devoted himself, as we see, to the most general problems of our science, refusing to let himself be diverted to more grateful and more easily attained ends. I have often heard colleagues try to attribute this attitude of his to extraordinary will-power and discipline – wrongly, in my opinion. The state of mind which enables a man to do work of this kind is akin to that of the religious worshiper or the lover; the daily effort comes from no deliberate intention or program, but straight from the heart.
Alexander Grothendieck had a similar view, expressed in the preface of Récoltes et Semailles:
Il est vrai aussi que l’ambition la plus dévorante est impuissante à découvrir le moindre énoncé mathématique, ou à le démontrer—tout comme elle est impuissante (par exemple) à “faire bander” (au sens propre du terme). Qu’on soit femme ou homme, ce qui “faitbander” n’est nullement l’ambition, le désir de briller, d’exhiber une puissance, sexuelle en l’occurence—bien au contraire!
Mais c’est la perception aiguë de quelque chose de fort,de très réel et de très délicat à la fois. On peut l’appeler “la beauté”, et c’est là un des mille visages de cette chose-là. D’être ambitieux n’empêche pas forcément de sentir parfois la beauté d’un être, ou d’une chose, d’accord. Mais ce qui est sûr, c’est que ce n’est pas l’ambition qui nous la fait sentir…
It is also the case that the most totally consuming ambition is powerless to make or to demonstrate the simplest mathematical discovery—even as it is powerless (for example) to “score” (in the vulgar sense). Whether one is male or female, that which allows one to ‘score’ is not ambition, the desire to shine, to exhibit one’s prowess, sexual in this case. Quite the contrary!
What brings success in this case is the acute perception of the presence of something strong, very real and at the same time very delicate. Perhaps one can call it “beauty”, in its thousand-fold aspects. That someone is ambitious doesn’t mean that one cannot also feel the presence of beauty in them; but it is not the attribute of ambition which evokes this feeling…
Ernst Mach did not believe in the physical reality of atoms, in opposition to Planck. Even in 1910, 5 years since Einstein’s Brownian motion paper, Mach wrote:
The essential difference between us concerns belief in the reality of atoms… My answer is simple: If belief in the reality of atoms is so crucial, then I renounce the physical way of thinking, I will not be a professional physicist, and I hand back my scientific reputation. In short, thank you so much for the community of believers, but for me freedom of thought comes first.