In this paper, Thomas has explored 3 Hypotheses respecting the past history of Nature. He presented positive and negative evidence ( testimonial and circumstantial evidence) to establish the possibility of the conclusion.
The first Hypotheses was less reliable as people argued that Nature is unchanged from the first beginning to the present, i.e. Nature is eternity. It is easy to see that there is not an eternity of witness and no infinity of circumstances to present any evidence to prove the eternity. From the beds of Stones and fossils found, we can see that there are similar species to modern species; while the lower tertiaries, from Mesozoic rocks to Paleozoic formations, there is less and less species that resemble similar feature of modern species. In the Stratified rocks, there is no indication of life as far as we can see.
The second Hypotheses was popular among God believers. They believe God create the Nature in Six days and thus present was not similar to the past at all (see the Genesis in Bible or Milton’s Paradise Lost). Thomas named this Hypotheses as Milton’s Hypotheses which to avoid misunderstanding of attaching Christianity. From the fossil found there is no evidence of discontinuity in natural processes. I personally don’t believe God create everything in six days.
The last Hypotheses, while the ever famous, is the Hypotheses of evolution. Thomas presents both the favorable/neutral evidences and negative indifferent evidence. The difficulties were in proving there is moderated changed from the past to present, when is he evolution starts and how to establish bridge between species. From mummified bodies and the examination of lizard, it is hard to see trace of difference and mortification. But it may due to the fact that mortification might go through much longer time than we thought, imperfection of geological record and lack of factors to provoke evolution (tendency to vary and influence of surrounding condition).
If evolution did happen, how to explain why mammals, birds and reptiles have distinctive features? With more and more evidence found, we may have more confidence to support the possibility of evolution. Thomas has given several ancient species that might fill the gap of pig tribe and ruminants, and, bird and reptiles.
some quote from the essay:
With relation to this universe, man is, in extent, little more than a mathematical point; in duration but a fleeting shadow, he is a mere reed shaken in the winds of force. But as Pascal long ago remarked, although a mere reed, he is a thinking reed; and in virtue of that wonderful capacity of thought, he has the power of framing for himself, a symbolic conception of the universe.
Human belief, however broad its basis, however defensible it may seem, is, after all, only a probably belief, and that our widest and safest generalization are simply statements of the highest degree of probability.
Cautious men will allow that a universe so different from that which we know may have existed; just as a very candid thinker may admit that a world in which 2 and 2 do not make four and in which 2 straight lines do inclose a space, may exist.