Callicott's justification for this claim is an analysis based on the following criteria for tenability: self-consistency; comprehensiveness; self-correction; universality; and beauty. The first test of a scientific worldview is logical self-consistency and the evolutionary-ecological worldview passes that test. A tenable scientific worldview must comprehend all known facts and so far the evolutionary-ecological worldview does account for all the facts, such as the existence of the fossil remains of extinct species. When the details of that worldview are shown to be inconsistent with themselves or unable to account for all the facts, the theory is revised accordingly; the evolutionary-ecological worldview is thus self-correcting and is therefore, Callicott believes, becoming ever more refined. The evolutionary-ecological worldview has global currency and enjoys international credibility; that is, it has universal appeal. And finally, as to beauty, Darwin himself observed in the final sentence of the "Origin" that “There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.”