Can we agree that a stone is not alive? Let's not say "dead" because that implies once lived. It has no dynamic, does not interact or act with purpose of self-sustenance. Maybe it is the ability to reproduce that is definitive, although in theory something could be alive, having come to life and never died and never reproduced. A stone came to being but never reproduced itself and did not interact purposefully with anything, had no self-sustaining or any continuing process in which it was active. Then again, there are machines that are active and interact continually and purposefully, like those robots that go around and around vacuuming the floor, but are they alive? Intuitively no, so what are they lacking that for example a microbe inside a rock has? To make a self-reproducing robot is a major challenge, which as far as I know has never been achieved, but would we think that those robots were alive, if they were able to reproduce and perhaps even sustain themselves for a while? (not "indefinitely", or else the dinosaurs were never alive).
Maybe that's all there is to it: self-reproducing robots. There was a TV debate about religion (Christianity 2000 with Melvyn Bragg) where somebody in the audience argued against clerics on the panel that people were just like robots, to which the panellist replied well do you think that you are a robot and the speaker in the audience asserted that he (the speaker) was indeed a robot. It was very strange to hear somebody state in that way, "I am a robot" - almost as if it made that person into a robot by self proclamation, as if one could be or not be a robot by choice. There was a sense that that person had alienated himself from the entire audience and panel and got into a very weird situation.
But back to "What is life?" I think we can agree that a rock is not alive. If so, I guess we can also agree that a jar of acid is not alive. What if it's a jar of amino acid (some organic molecules)? We're told that DNA is made up of codes for a set of amino acids. When talking about robots and self-reproducing robots and acting purposefully for self-sustenance and continuation, what hasn't been discussed here yet is energy and motivation. We have material, sure, and we have "a scenario" (things act, reproduce, interact) but what is it that tells them how to behave, what to do and when: what starts them on a path and what guides their behaviour? (Turning straight to motivation and skipping the question of energy which is obviously just another mechanism, equivalent to the components of the robot.)
If we are agreeing that a jar of acid is not alive, is equivalent to a rock, and if we take it that DNA is code for a number of amino acids, then we are looking at a plan for items that are not in themselves inherently alive. We know that this pattern (DNA) is in living creatures ("duh") and we observe meiosis and all the events that cause half of one creature's DNA to combine with half of another creature's (for example - leaving cloning aside for the time being). We have, very obviously, the energy to power these processes. We have chemicals, patterns for chemicals and components, we can observe behaviour and formation of quasi-live spermatazoa (a form of life with a half-set of DNA, that looks and moves like plankton, say, but is humanoid?) but there is absolutely no explanation offered as to why these components proceed through very long processes (9 months in the human) of almost unimaginable complexity with clear purpose to create structures and creatures with inbuilt instincts, behaviours of their own and a big ETC.
What part of the weaver bird's DNA comprises the design of its nest and the talent and ability to create that nest from available materials in a timely way to provide a home for more little weaver birds? Hello, you've told us so far about amino acids.
Darwin deals with some of this in his section on instinct, in the chapter on objections to his theory. He didn't know about DNA, so he just assumed there was some mechanism in which behaviour could be inherited and gradually modified. His paragon of instinctive behaviour was bees constructing a honeycomb, which comprises a mathematically complex structure of interconnected hexagonal (?) cells. He broke it down to each bee digging out some of the wax and neighbouring bees doing the same till a thin line remained between the holes being dug by each of the neighbouring bees. The evolutionary principle kicked in because the honeycomb structure is the form that can contain the most honey with the least wax, and so bees that tended to make that shape thrived more than ones that didn't. Plus there are different types of bees that have less perfect combs, sort of transitional ones in isolated places etc. But even knowing about DNA and epigenetics, it's still hard to see how behaviour could be encoded.