What need is there for a god to exist?
The need for God exists because there is a vast range of human problems that the scientific method cannot even begin to address. Here's some "evidence" I've drawn on in support of this statement.
“Science without religion is lame, religion without science is blind.”So wrote Albert Einstein in 1941 to explain his personal creed: “A religious person is devout in the sense that he has no doubt of the significance of those superpersonal objects and goals which neither require nor are capable of rational foundation.” Einstein recognized himself as a deeply religious person in this sense. For Einstein, faith and reason were not separable, let alone mutually exclusive.
That doesn't mean that he injected God or a specifically religious view into his work as a scientist. Rather, his entire working presupposition was that "There had to be something behind objects that lay deeply hidden ... the development of [our] world of thought is in a certain sense a flight away from the miraculous." That is, he recognized that the universe, though seemingly incomprehensively vast and unfathomably complex, has the property of intelligibility, which presupposes Mind. (Which, by the way, it wouldn't have, if it were a random development out of chaos.)
His great biographer Abraham Pais, a distinguished physicist in his own right, [Subtle Is the Lord] wrote of Einstein:
... already as a young man, nothing could dissuade him from his destiny, which with poetic precision he put in focus at the age of eighteen: "Strenuous labor and the contemplation of God's nature are the angels which, reconciling, fortifying, and yet mercilessly severe, will guide me through the tumult of life."Anyhoot, that would be the view from the standpoint of one of the greatest scientists who ever lived. He doesn't speak for all scientists, of course. Jacques Monod, for example, would very likely not agree. But Newton would very likely have agreed with Einstein.
There's a more "common sense" level where the need for God is evident (to me at least):
At the level of common sense, it is evident that human beings have experiences other than sensory perceptions, and it is equally evident that philosophers like Plato and Aristotle explored reality on the basis of experiences far removed from perception. The Socratic "Look and see if this is not the case" does not invite one to survey public opinion but asks one to descend into the psyche, that is, to search the reflective consciousness. Moreover, it is evident that the primarily nonsensory modes of experience address dimensions of human existence superior in rank and worth to those sensory perception does: experiences of the good, beautiful, and just, of love, friendship, and truth, of all human virtue and vice, and of divine reality. Apperceptive experience is distinguishable from sensory perception and a philosophical science of substance from a natural science of phenomena. Experience of "things" is modeled on the subject-object dichotomy of perception in which the consciousness intends the object of cognition. But such a model of experience and knowing is ultimately insufficient to explain the operations of consciousness with respect to the nonphenomenal reality men approach in moral, aesthetic, and religious experiences. Inasmuch as such nonsensory experiences are constitutive of what is distinctive about human existence itself — and of what is most precious to mankind — a purported science of man unable to take account of them is egregiously defective. — Ellis SandozA hundred years after Einstein’s pioneering work, his sense of the inseparability of faith and reason has been almost entirely lost, supplanted by materialist, positivist, and rationalist dogmas that together comprise a doctrine of philosophic materialism that has penetrated to the very heart of modern-day science (and thus of so much else). The essential complementarity of faith and reason that Einstein recognized has been recast as the triumph of the rational (reason) over the irrational (faith).
Yet if Einstein is right, there really are superpersonal objects and goals “which neither require nor are capable of rational foundation." There really are nonsensory experiences. Any attentive student of history can tell you that such objects and goals and experiences have informed the conduct and progress of human life from time immemorial.
Such nonsensory modes of experience lie entirely outside the reach of the scientific method as presently constituted: methodological naturalism. But the fact that science cannot reach them does not mean they do not exist in Reality.
Which is not to say that I want to inject God or religion into science. He's already in it; for human reason itself utterly depends on the divine Logos. I just think it would be nice if scientists did not blindly rule Him out of the "initial conditions" of the universe; and I sure do wish they'd stop "politicizing" science in service of atheist presuppositions.
Politicized science is not any longer science.