The old die not to be replaced by the new but to become them. Molecule by molecule our corporeal selves traverse many a form and many a form traverse through us. Understand that all are the same and that our capacity to understand this is more by chance than by choice.
Our capacity to understanding what life is, is limited only by our disability to think in vast measures. Geological time perplexes us as much as complex mathematics can. Any counter-intuitively large quantity is as hard to grasp for an adult as complex mathematical formulations are hard to grasp for a child. We can look at a large number and only try to grasp it by either dividing it in comprehendible chunks or by finding visual analogies that fit its proportions.
Our inherently human limitations are why we have tools and descriptors such as mathematics in the first place. They help us understand complexities in reality by formulating them in a clear and understandable scientific language.
The tool we use to describe life in its fundamentals is chemistry. “Life” is another word for extremely complex chemical paradigms. There is nothing of particular added value to the universe about the life on this planet. The chemical environment on this planet and indeed this part of our galaxy happens to be conducive for the emergence of chemical complexities we phrase as “life”.
As humans we can’t help but perceive the world through our evolved perceptions. We tend to attribute human emotional responses and emotionally perceived values to ourselves and life in general. This can be explained by considering the altruistic nature of this behavior. Giving preferences to subjects that help you not to eradicate yourself is inherent to all long term processes and “life” is not excluded in this distinction.
What can give added value to individual instances of “life” are the relative interactions they can have and contributions they make amongst each other in helping one another survive.
There are some that wish to proclame artificial temporal constraints for the start and end of “life”. When viewed from a limited perception “life” may seem to start at birth. An observer with a wider point of view may argue that “life” starts at the cellular merger called conception. One with an even wider perspective may argue that “life” started with our evolution on this planet. I would go one step further and state that the chemical complexity we call “life” emerged as the result of the event that brought forth the big bang.
Our determination of the start of our lives is much akin to the determination of the start of a tree. When is a tree a tree? At 1cm? At conception? When you can climb it? Any artificial starting point for the start of our life is just as arbitrary. No, what we as humans really mean with the “start of life” is “when does an individual’s presence contribute to our perceptions and emotions?”
We mourn the dead because they will be missed from our future experiences. We mourn because we miss the absent. Their emotional contributions will not be made as we would have wanted. In other words, because they’re gone from “life” and gone from our lives.
We humans have emotions that often limit our capacity for rational determinations of reality. This is the hurdle we must pass before being able to make such fundamental determinations about not just our reality, but about ourselves.
