The author’s conclusion that the ice sheet must have melted is not based on the idea that this view is widely believed to be true. We don’t know whether other people besides the author believe the ice sheet melted.

The author does not assume that the melting of the ice sheet could not have been produced by a combination of climatic warming and volcanic activity. The author presents those two things as potential causes for the melting, but never suggests they were mutually exclusive.

The author’s conclusion is that a certain event occurred — the ice sheet melted. The flaw relates to the author’s failure to prove that this event happened. The author did not establish this event occurred, and does not try to reach a conclusion about the cause of this event.

The claim that the ice sheet must have temporarily melted does not have “general application.” It is a claim about a particular ice sheet and that it must have melted around 3 million years ago. This does not apply to other ice sheets or other time periods.

The inconsistency is that we found 3-million-year-old fossils under the ice sheet, even though this kind of fossil has previously been found only in the ocean floor. The author thinks this must be because the ice sheet melted. This overlooks other explanations.