Mr. Graham Hancock in his book "The Mars Mystery" quotes Hoyle, "Origin of Universe"
I saw that the answer to this question lies in what is now called the anthropic principle, which says that the fact of our existence can be used to discount all improbabilities necessary for our existence. If history and civilization were caused by the arrival of a periodic giant comet, all accident is removed from our association in time with such a comet. The arrival of the comet was random but our association with the effects of the comet is not.
The paragraph is full of riddles for me. The hardest is "to discount all improbabilities necessary for our existence" I can understand the "improbabilities" word here, multiple quite rare natural conditions should be accomplished for the human civilization to appear and evolve. What I don't understand is why we shall 'discount' (=dismiss) such improbabilities. To the contrary, I would think we should justify them , make them more probable (none of the dictionaries I use gives even distantly similar to "justify" meaning to "discount")
Oft it is natural to follow the current of the author's thought. This particular instance for me is quite the opposite. Feel myself paddling upstream against strong current. The last sentence is the example (IMHO) of the strong disagreement between logics used in the sentence and what I got accustomed is applied in the life ^H^H^H^H common sense logic.