Complex sentence: Reformed epistemology grew out of the parity argument presented by Alvin Plantinga in his book "God and Other Minds" (1967): if belief in other minds is rational though unsupported by argument, so might belief in God be rational though similarly unsupported.
Split into simpler sentences: Reformed epistemology grew out of the parity argument presented by Alvin Plantinga in his book "God and Other Minds" (1967). There Plantinga concluded that if belief in other minds is rational though unsupported by argument, so might belief in God be rational though similarly unsupported.