In theology, the term Reformed implies a connection to the Protestant Reformation, especially the work of John Calvin. In philosophy, epistemology is the study of how we know things. Both ideas are connected to the field of Reformed epistemology, which applies core principles espoused by John Calvin to our assessment of religious or spiritual truths. This approach is not identical to presuppositional apologetics, but the two are closely related. The most notable contributors to discussions on this theory are Alvin Plantinga, Nicholas Wolterstorff, and William Alston.
A cornerstone of Reformed epistemology is the claim that belief in God is “properly basic.” Being “properly basic” means something is reasonable, necessary, and ultimately needs no prior proof. It can be assumed from the start and to some extent is even required for other thoughts to make sense. This implies that the existence of God is an assumption at the same logical level as that of our own existence, the validity of logic, and so forth.
The idea that God’s existence is properly basic is related to Calvin’s concept of the sensus divinitatis: the claim that all people have some innate perception of God. So far as Reformed epistemology is concerned, belief in God is considered justified—acceptable or reasonable—without resort to any particular argument or evidence.
As one can imagine, this is a controversial claim, with debates on the subject occurring both within and across religious perspectives. A common criticism of this stance is that it amounts to fideism: a choice to believe “just because, no matter what.” However, Reformed epistemology qualifies acceptance of even properly basic beliefs as needing to be defended against reasonable objections or questions.
A primary application of Reformed epistemology apologetics is the suggestion that justified knowledge comes from human intellectual abilities that are functioning according to their intended design. This, of course, implies there is some intended design, which is derived from a theistic God.
Reformed epistemology differs from presuppositional thinking in subtle ways. Typical presuppositionalism interprets the sensus divinitatis as a literal “awareness” of God: that all people intrinsically know God exists. Reformed epistemology sees the sensus divinitatis more as a tendency or capacity than as a point of cognitive awareness. Presuppositional apologetics embraces the idea that all logical arguments are eventually circular; therefore, there can be no real “common ground” between the believer and non-believer. Reformed epistemology takes a less strident view of that divide. Likewise, presuppositional views imply that rational discussion is ultimately impossible without theistic assumptions, another area in which Reformed epistemology takes a less-firm stance.
There are also differences between Reformed epistemology and schemes such as foundationalism. Rather than suggesting that cornerstone beliefs need to be “highly certain,” even “self-evident,” as in classic foundationalism, Reformed epistemology allows for more flexibility, and is therefore an example of reliabilism. Given that it accepts beliefs as justified, even if there is no explicit evidence, Reformed epistemology is opposed to exclusively evidentialist views of justification or apologetics.