What is the word *then* doing in "The constant synthesis, **then**, of specific material from simple....",?

Question

It was usually considered that the most characteristic feature of life is its metabolism.

" The constant synthesis, then, of specific material from simple compounds of a non-specific character is the chief feature by which living matter differs from non-living matter"

,was the way it was expressed by Jacques Loeb in 1916

What is the word then between commas doing?, is it describing time or anything else?

My rephrasing of quoted text is that synthesis of specific material from compounds that are non specific nature is the difference between organic and inorganic If my above rephrase is wrong, I would really appreciate if anyone can rephrase the quoted text in simpler form

Answer 1

It is expressing that what he is saying in that sentence is the consequence of something he said previously. He could have started the sentence with then, or he could have used so:

So, the constant synthesis... is the chief feature...

Merriam-Webster then

adverb : as it appears : by way of summing up
the cause of the accident, then, is established

The M-W example could also be rephrased

So, the cause of the accident is established.