Einstein was a fairly strong agnostic, and fundamentally a Naturalist of sorts..
From:
Religious and philosophical views of Albert Einstein - Wikipedia
"Einstein called himself an agnostic rather than an atheist, stating: "I have repeatedly said that in my opinion the idea of a
personal god is a childlike one. You may call me an agnostic, but I do not share the crusading spirit of the professional atheist whose fervor is mostly due to a painful act of liberation from the fetters of religious indoctrination received in youth. I prefer an attitude of humility corresponding to the weakness of our intellectual understanding of nature and of our own being."
[13] In an interview published by the German poet
George Sylvester Viereck, Einstein stated, "I am not an Atheist."
[10] According to
Prince Hubertus, Einstein said, "In view of such harmony in the cosmos which I, with my limited human mind, am able to recognize, there are yet people who say there is no God. But what really makes me angry is that they quote me for the support of such views."
[26]
In 1945 Guy Raner, Jr. wrote a letter to Einstein, asking him if it was true that a
Jesuit priest had caused Einstein to convert from atheism. Einstein replied, "I have never talked to a Jesuit priest in my life and I am astonished by the audacity to tell such lies about me. From the viewpoint of a Jesuit priest I am, of course, and have always been an atheist. ... It is always misleading to use anthropomorphical concepts in dealing with things outside the human sphere—childish analogies. We have to admire in humility the beautiful harmony of the structure of this world—as far as we can grasp it, and that is all."
Afterlife:
On 17 July 1953 a woman who was a licensed
Baptist pastor sent Einstein a letter asking if he had felt assured about attaining everlasting life with the Creator. Einstein replied, "I do not believe in immortality of the individual, and I consider ethics to be an exclusively human concern with no superhuman authority behind it."
[31] This sentiment was also expressed in Einstein's book
The World as I See It (1935), "I cannot conceive of a God who rewards and punishes his creatures, or has a will of the type of which we are conscious in ourselves. An individual who should survive his physical death is also beyond my comprehension, nor do I wish it otherwise; such notions are for the fears or absurd egoism of feeble souls. Enough for me the mystery of the eternity of life, and the inkling of the marvellous structure of reality, together with the single-hearted endeavour to comprehend a portion, be it ever so tiny, of the reason that manifests itself in nature."