What is a "Plausible Evolutionary Pathway"?

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I hear the following phrase quite a bit- "Plausible evolutionary pathway"- It is used wrt any biological feature that cannot be directly/ experimentally tested to see how it could arise.

For example with bacterial flagellum's evos say there are plausible evolutionary pathways that could account for their existence. However these plausible pathways can't be tested to see if they are plausible.

What's the point? Well it seems that when someone sez there is a "plausible evolutionary pathway" they mean someone imagined a pathway and told someone else.

Yup, I know what yuou are saying "All science so far!" LoL! But THAT is it. Evos really think that if someone can imagine a pathway then that is really all they need. Ya see no one will be able to prove them wrong. However what they fail to realize is "That which can be asserted without evidence can be dismissed without evidence"- Hitchens. And imagination is not evidence.

So the bottom line is when someone sez there is a "plausible evolutionary pathway", get ready for a load of bullshit.