In the 1988 version Barbour listed two subtypes: doctrinal reformulation and systematic synthesis. In the 1990 version, the primary examples of doctrinal reformulation were recategorized as ‘theology of nature’ and he separated them off from what he now calls ‘natural theology.’ The term ‘theology of nature’ is roughly equivalent to what others call ‘constructive theology in light of science.’ Similarly ‘integration’ is frequently called ‘interaction.’