Perhaps the largest body of work, however, was generated in dialogue with the linguistic turn of philosophy in the English-speaking world, concentrating on the analysis of language in its various uses. The logical positivist movement originated in the 1920s with the Vienna Circle. Although mainly concerned with the philosophy of science, it posed by implication a major challenge to the logical meaningfulness of religious language. The positivist position, in its developed form, was that a statement has factual meaning only if it is capable in principle of being verified or falsified, or at least in some degree confirmed or disconfirmed, within human experience; otherwise it is meaningless, or cognitively vacuous. In the years immediately after World War II this account of factual meaning was applied (e.g., by Antony Flew) to theological statements, raising such questions as: What observable difference does it make whether it is true or false that “God loves us”? Whatever tragedies occur, do not the faithful still maintain their belief, adding perhaps that the divine love is beyond human comprehension? But if it is not possible to conceive of circumstances in which “God loves us” would have to be judged false, is not the statement factually empty, or meaningless?
This challenge evoked three kinds of response. Some Christian philosophers declared it to be a nonchallenge, on the ground that the positivists never succeeded in finding a precise formulation of the verification criterion that was fully satisfactory even to themselves. Others held that this does not block the central thrust of the positivist challenge. Does it really make no difference within actual or possible human experience whether or not God exists and loves us; and if so, is not the significance of the belief thereby fatally damaged? Among those who felt it necessary to face this challenge, one group granted that theological statements lack factual meaning and suggested that their proper use lies elsewhere, as expressing a way of looking at the world (e.g., Richard M. Hare) or a moral point of view and commitment (e.g., R.B. Braithwaite). The other group claimed that theism is ultimately open to experiential confirmation. The theory of eschatological verification (developed by John Hick) holds that the belief in future postmortem experiences will be verified if true (though not falsified if false), and that in a divinely governed universe such experiences will take forms confirming theistic faith. Thus although the believer and the disbeliever do not have different expectations about the course of earthly history, they do expect the total course of the universe to be radically different.
In the late 20th century, under the stimulus of Wittgenstein’s posthumously published works, attention was directed to the multiple legitimate uses of language in the various language games developed within different human activities and forms of life; and it was suggested that religious belief has its own autonomous validity, not subject to verificationist or scientific or other extraneous criteria. Statements about God and eternal life do not make true-or-false factual claims but express, in religious language, a distinctive attitude to life and way of engaging in it. This suggestion formed part of the broader non-realist interpretation of religion, which held that religious beliefs do not refer to putative transcendent realities but are instead expressive of human ideals, desires, hopes, attitudes, and intentions. Such thinking goes back to the German philosopher Ludwig Feuerbach (The Essence of Christianity, 1841) in the 19th century. It was promoted in the early 20th century by George Santayana, John Dewey, and J.H. Randall, Jr., and later by Christian writers such as D.Z. Phillips and Don Cupitt. According to them, true Christianity consists in the inner purity of an unself-centred attitude to life and does not involve belief in the objective reality of God or of a life after death. This view, however, was criticized on the grounds that to deny the transcendent reference of religious language empties it of any substantial meaning. Evidentialist approach
In addition to this and other work concerning religious language there was a renewal of fundamental discussion of Christian, and more broadly religious, epistemology. The natural theology tradition held that, in order to be rational, religious belief must be supported by adequate evidences or arguments. It was assumed that God’s existence must be validly inferred from generally acceptable premises. This evidentialist principle was questioned, however, not only by such earlier thinkers as Pascal and William James but also by a number of Christian philosophers of the second half of the 20th century. Evidentialist thinking was foundationalist in granting that there are some beliefs that can be reasonably held directly and not by inference from other evidence-stating beliefs. Thomas Aquinas, for example, recognized self-evident truths and the reports of the senses as basic in the sense that they do not need support from other beliefs. They thus provide the foundations on which a belief structure can properly be built. Belief in the existence of God was not regarded as basic or foundational in this way but was thought to require adequate evidence or arguments. It was argued by Alvin Plantinga that the range of properly basic beliefs is wider than classic foundationalism recognized. It can include not only beliefs about the past and the existence of other persons but also belief in the reality of God. Such beliefs can be basic (i.e., not inferred), and they are properly basic if held in appropriate circumstances. Thus, the belief that “There is a tree before me” is properly basic for one who is having the experience of seeing a tree; and the belief that “God exists” is properly basic for one who experiences God’s judgment, forgiveness, love, claim, providential care, or some other mode of divine presence.
Discussion of this proposal centred upon the criteria for proper basicality: In what circumstances is it appropriate, and in what circumstances not, to hold the basic belief in God or the basic beliefs of other religions or of the naturalistic worldviews?
A related contemporary development, pursued by William Alston and others, is the claim that religious experience constitutes an entirely proper basis for religious beliefs. The claim is not that one can validly infer God as the cause of theistic religious experience, but that one who participates in such experience is entitled to trust it as a ground for belief. It was argued that human beings all normally operate with a “principle of credulity” whereby they take what seems to be so as indeed so, unless they have some positive reason to doubt it. Accordingly, one who has the experience of living in the presence of God can properly proceed in both thought and life on the basis that God is real. Such belief inevitably involves epistemic risk—the risk of error versus the risk of missing the truth. But perhaps the right to believe that was defended by William James applies in this situation.
The discussion focused on the analogies between religious experience and sensory experience in relation to which the principle of credulity is virtually universally accepted. It is uncontroversially proper to hold beliefs reflecting sense experience, but what of beliefs reflecting religious experience? Whereas all human beings hold the former and could not survive without doing so, the latter type of belief seems to be optional. Although beliefs regarding physical objects can be empirically confirmed or denied, religious beliefs cannot. Acknowledging these differences, some Christian philosophers argued that they are to be expected, given the difference between the human relationship to the world and to God. It is necessary to human existence as physical organisms that consciousness of the material environment should be forced upon human beings. On the other hand, it is necessary for existence as relatively autonomous and responsible beings that consciousness of God should not be forced upon them, for to be compulsorily aware of God’s universal presence as limitless goodness and power, making a total claim upon human life, would deprive them of creaturely freedom. Humans are accordingly set at an epistemic distance from God that is overcome only by faith, which can be identified with the voluntary interpretive element within the experience of God’s presence.