From “We Have Reason to Believe” by Louis Jacobs:

“In the nature of the case, the evidence of the senses cannot
demonstrate the existence of that which is not the senses, nor can the
effort of the human intellect demonstrate the existence of that which
is more than the human intellect. To say this is not to surrender
reason – this would be suicidal, for unreliable as the human reason
may be, it is the only instrument we have for testing truth – but a
recognition, in the name of reason itself, that we must look beyond it
for the apprehension of certain truths. In other words a distinction
must be drawn between proof and conviction – proof is
one of the ways to conviction but there are other ways too. So that
the real question is not whether the existence of God can be proven
but whether belief In His existence is overwhelmingly convincing.

Many have arrived at this conviction as a result of a personal
experience which convinces them that God exists, for, they would say,
a man who is truly in love, he does not ask himself if he is in love.
The experience of God’s Presence is sufficient. This is the
mystical approach to religion, the approach of the Besht, the founder
of the Hasidic movement, who was fond of quoting the verse: “Taste ye
and see that the Lord is good”. Religious experience, he said, is
compared to tasting food – the taste cannot be conveyed, it must be
experienced. The Hasidim tell of one of their leaders who once
startled his followers sitting with him at table, by asking them: “Do
you believe in God?” “Rabbi”, was their horrified reply, “of course we
believe in God.” “Well I do not”, said the Rabbi. And he went on to
explain: Do you believe that we are sitting at a table? You
know we are sitting at a table”. It is said that in one of the
African dialects, deficient in names for abstract ideas, the nearest
to the word “believe” is “to hear in the heart”!

But this approach cannot be of much help to one who has never had an
experience of this nature, though there is valuable evidence for the
truth of the religious hypothesis in the remarkable unanimity in which
those who claim to have had mystical experience record that
experience. The mystics of quite different ages and climes all seem to
have “seen” the same vision. And very many people, far removed from
the conventional picture of the mystic, claim to have had a similar
experience, to “know” that God exists.

In recent years, the religious Existentialist movement has won many
adherents. This movement considers the attempt to prove the existence
of God as an impertinence. God must be encountered. We cannot
calmly discuss whether God exists as if we were debating an
intellectual puzzle which has no relevance to our lives. If we are to
experience religious truth we must take what Kierkegaard calls “the
leap of faith”, we must respond with our whole being to the call of
God, we must be personally committed, and only then will God reveal
Himself to us. The Jewish existentialist approach can be studied
espcially in the works of Martin Buber and Franz Rosenzweig and their
disciples.

Many religious thinkers, on the other hand, still favour a “rational”
approach to religious belief, convinced that the final word has not
been had on the subject by the Kantians. Kant himself was convinced of
God’s existence because of the pricking of human conscience – the
“voice of God” – in the human breast. In an oft-quoted passage, Kant
remarks: “Two things fill me with mind with ever-increasing wonder and
awe, the more often and the more intensely the mind of thought is
drawn to them: the starry heavens above me and the moral law within
me.”

The late Chief Rabbi of Palestine, Rav Kook, one of the profoundest
modern Jewish religious thinkers, went so far as to say that obedience
to the moral law was itself obedience to God, even if not recognised
as such. Thus he remarked that the religious person ought not to feel
disturbed of dismayed when he sees people without any kind of
religious affiliation working for social justice, for these men are
“doing God’s work without knowing it”. (“Letters”: No. 44)

The point is also worthy of note that the urge to worship in the human
breast affords evidence of God’s existence. “Man must worship
something; if he does not worship God, he will worship an idol made of
wood or of gold or of ideas”. (Dosetoievsky)

Other thinks, again, hold that though each of the tradition proofs in
itself are unconvincing, taken together they are convincing. For the
Kantian objections are not complete refutations of the proofs. They do
no more than demonstrate the weakness of each of them taken by itself.
Granted that the proofs carry no weight as evidence, they are
indications and as such have the power of supplementing each
other.

Sir Arthur Eddington has finely said: “Theological or anti-theological
argument to prove or disprove the existence of a deity seems to me to
largely occupy itself with skating among the difficulties caused by
our making a fetish of this word. It is all so irrelevant to the
assurance for which we hunger. In the case of our human friends we
take their existence for granted, not caring whether it is proven or
not. Our relationship is such that we could read philosophical
arguments design to prove the non-existence of each other, and perhaps
even be convinced by them – and then laugh together over so odd a
conclusion. I think that is something of the same security we should
seek in our relationship with God. The most flawless proof for the
existence of God is no substitute for it; and if we have that
relationship, the most convincing disproof is turned harmlessly aside.
If I may say it with reverence, the soul and God laugh together over
so odd a conclusion”. “