Implicit and explicit atheism

Implicit atheism and explicit atheism are types of atheism coined by George H. Smith (1979, p. 13-18). "Implicit atheism" is defined as "the absence of theistic belief without a conscious rejection of it", while "explicit atheism" is "the absence of theistic belief due to a conscious rejection of it". Explicit atheists have considered the idea of deities and have rejected belief that any exist. Implicit atheists, though they do not themselves maintain a belief in a god or gods, have not rejected the notion or have not considered it further.

Smith defines "implicit atheism" as "the absence of theistic belief without a conscious rejection of it". "Absence of theistic belief" encompasses all forms of non-belief in deities. This would categorize as implicit atheists those adults who have never heard of the concept of deities, and those adults who have not given the idea any real consideration. Also included are agnostics who assert they do not believe in any deities (even if they claim not to be atheists). Children are also included, though, depending on the author, it may or may not also include newborn babies. As far back as 1772, Baron d'Holbach said that "All children are born Atheists; they have no idea of God". Smith is silent on newborn children, but clearly identifies as atheists some children who are unaware of any concept of any deity:

The man who is unacquainted with theism is an atheist because he does not believe in a god. This category would also include the child with the conceptual capacity to grasp the issues involved, but who is still unaware of those issues. The fact that this child does not believe in god qualifies him as an atheist.

Ernest Nagel contradicts Smith's definition of atheism as merely "absence of theism", acknowledging only explicit atheism as qualifying for the label "atheism":

I shall understand by "atheism" a critique and a denial of the major claims of all varieties of theism... atheism is not to be identified with sheer unbelief... Thus, a child who has received no religious instruction and has never heard about God, is not an atheist – for he is not denying any theistic claims. Similarly in the case of an adult who, if he has withdrawn from the faith of his father without reflection or because of frank indifference to any theological issue, is also not an atheist – for such an adult is not challenging theism and not professing any views on the subject.

Smith observes that some motivations for explicit atheism are rational and some not. Of the rational motivations, he says:

The most significant variety of atheism is explicit atheism of a philosophical nature. This atheism contends that the belief in god is irrational and should therefore be rejected. Since this version of explicit atheism rests on a criticism of theistic beliefs, it is best described as critical atheism.

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