system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:What makes something alive?

I've been always wondering. Can life be artificial? If I put a skeleton, organs, skins together and run the appropriate electricity frequency through that "body". Will it function or not? If not, why? Lack of soul?
gpt
There are a number of different definitions for what it means to be alive and the truth is that for the most part there is no clear line we can draw between dead things and living thing to separate them because there are a lot of things in between and the transition is a more gradual than most people would think.

The Frankenstein process you gave in your example is the sort of thing we can do to a degree. When for example doing a heart-lung transplant we take parts from what are essentially at that point two dead people, stitch them together and revive the creature we made that way.

Naturally the person who received the transplant was only mostly dead before he got the new heart and lung. They were not breathing and their heart was not beating (on account of both the heart and lung having been cut out), but the rest of the body was still alive.

If you had asked somebody a few centuries ago they would have told you that lack of heartbeat and not breathing meant that somebody was dead, but  we resuscitate people with that all the time nowadays.

We look at things like if enough of the cells that make up the body especially those in the brain are still alive to determine if a person is alive, only technically dead or really dead.

If the cells that make up the organ are alive then the organ is still alive and when the vital organs are still alive the patient can be considered to be sort of alive. Of course the brain is the most important part and if enough of the cells in it have died to destroy the parts that encode a humans personality than the rest of the body may be as alive as it can be, but the patient is braindead.

Souls generally don't enter into the equation because nobody has ever been able to tell how one would test for one.

In the past there were some religious people who claimed that children conceived in vitro (so called test tube babies) didn't have any soul, but since the procedure nowadays is pretty common and there are plenty of people walking around conceived that way, few people are still willing to make such claims.

For humans we mostly care about having brains that still work and enough of a body to keep them that way.

A decapitated head is technically still alive for a short while and the person in question may or may not even be conscious for a short moment but there isn't really anything we can do with today's medicine to stop death from completely claiming them.

On a different level we have similar problem in determining when something qualifies as a living thing We know that animals, plants, fungi and bacteria are alive, but we have more trouble classifying such things as viruses or prions which have many of the same qualities as living things but lack others.

It is often necessary to draw a line somewhat arbitrary even though examples on both sides of that line may look very similar to one another.

What is worse is that we can see what we would normally ascribe only to living things in very different contexts. We have computer viruses and similar digital creations which are obviously not alive even though they manage to tick some of the checkboxes for living things and we even have such things as memes which are just ideas but nonetheless can evolve like living things.

We can't really say when life ends in such a way that we can't bring it back, we can say what cleanly separates living things from dead things and everyone know the trouble we get when we try to define when human life begins from the abortion debate.

Nothing of it is as easy and clear cut as we might wish and most of the difference between dead and alive are gradual transitions rather on/off switches.

Life is complicated.