(Original post by Mubariz)
No, they do not know what life is, you can just classify what is alive and what isn't.
If we didn't know what life is, we wouldn't be able to say "this is alive" and "this is not". To say that something has life, you need to know what life is first. Just like I couldn't tell you that you have eyes if I didn't know what eyes were.
What makes something live?
Its genes. Life is simply a culmination of functions. There's no magic going on here. No life force, no soul, nothing imbued by a higher deity. What we have are sets of molecules interacting electromagnetically.that produce functions.
What made the first thing live?
Due to the lack of an unequivocal definition of life, you'd have a hard time deciding what the first living thing even was. However, life exists as it is today because its ancestors were better suited than their competition to replicate in the environment. We don't understand the actual chemistry of what happened - what the mechanism of the creation of the last universal common ancestor was, but we can postulate that it was a result of natural selection. Natural selection applies to any kind of replicator, and not just living ones.
That said, our lack of understanding of its origins does not take away from the scientific nature of study of life. Just like cosmologists study the universe, but don't know its origins.
Definition of life "Life is a characteristic that distinguishes objects that have self-sustaining biological processes ("alive," "living"), from those which do not"
Clearly a circular definition, now aside from this, scientists themselves cannot fully agree on what the definition of life is, some would say the 7 things "MRSNERG" but some say that you require brain activity etc.
You can't just say "clearly a circular definition", and not justify it. A circular definition is any definition which presupposes itself. "Life is anything that is alive" would be a circular definition. The definition we have is "Life is a set of X characteristics". Nothing circular there. We just struggle to decide what exactly "X" should be.
Equivocal definitions are a facet of all
aspects of science. Biology is not alone in possessing these. That's simply part of the epistemological constraints placed on us by the fact that we're human.
Comparing "MRS GREN" to brain death is misunderstanding the context of the word "life" in both discussions. They're used in two different contexts and carry two different meanings.
Biologist classify living organisms by a hierarchy of taxonomies: species, phylum etc etc but again biologists cant tell us what a species is or phylums are
Taxonomy is irrelevant to the discussion of life. It's a method of classifying organisms, rather than life. Simply Googling the words "species" and "phyla" will tell you what they are. We know quite well what they are. We invented the words.
of course it is simplified, I'm not going to write out or copy the whole scientific method
Laws of Thermodynamics, Newtons Laws, Etc
Yes. Not all science culminates in the production of a scientific law. There are laws within science, but the production of laws are not defining feature of science. This is simply because the definition of "law" can't stretch to encompass all knowledge that the scientific method produces.