Lifeforms

I don't consider human individuals to be lifeforms.

This includes myself.

Definition of a lifeform. I define a lifeform as something meeting both of the following criteria:

it must be capable of existing and continuing to exist, which is to say it must constitute a System for Continued Existence;
it must be capable of expanding without limit to consume all available resources.

Criterion (1) above does not mean that something has to actually prevail to constitute a lifeform. A lifeform can go extinct and still be considered a lifeform. However, it must have some theoretical design capability to exist perpetually, conditions permitting.

A human individual meets neither of these criteria:

a human individual has a finite lifespan (and is incapable of asexual reproduction), and so in and as of themselves cannot constitute a System for Continued Existence;
a human individual grows to a finite size and has a finite resource consumption capacity.

The human species meets both of these criteria:

the human species can restore itself via subsequent generations in perpetuity;
the human species, by increasing its population, can scale arbitrarily and without limit to consume all available resources.

A subset of the global human population can also constitute a lifeform in itself, so long as biodiversity requirements are met (i.e., a man and a woman alone probably do not constitute a lifeform).

Motivation for this definition. My basis for adopting and using this definition is that the object of evolution is necessarily to give rise to Systems for Continued Existence. This, in itself is an inevitability owing to the nature of the universe itself (or perhaps, quite possibly, due to the nature of reality itself — which is to say that this property possibly necessarily pervades all possible universes with all possible laws of physics, not merely this universe with its particular laws of physics. This is not to state that I necessarily believe in multiverses, I'm simply stating that even if there could exist hypothetically some alternate universe with a different law of physics, it seems like some fundamental parameters of reality would need to stay the same, as far as anyone can tell, anyway):

We live in a universe of things which exist, which contains only things which exist and not things which don't exist.
Analogously to the anthropic principle therefore, it's not surprising that we find that we exist and that we find in this universe other things that exist.
Since the universe only contains things which exist, the things which exist in it by and large will be things which are good at existing.

Some things might arise in the universe which are good at not existing, but these things are likely to cease to exist almost as soon as they come into existence, making us unlikely to notice them.

Some lifeforms might be unmotivated to exist but at the same time not motivated to not exist, but we might imagine that these existences probably wouldn't exist very long before their indifference to nonexistence erases them.
Therefore, any organism arising in this universe of things that exist (long enough for us to notice it) necessarily must seek to survive, and any system of evolution arising in this universe of things must exist must inexorably program its subjects with an urge to survive.

In other words, the biological imperative of survival is an inevitable consequence of the nature of the universe itself, or even of reality wholesale, independent of any specific law of physics.
In this regard, the essential objective of evolution can be considered to give rise to things which are good at existing; that is, Systems for Continued Existence.
I therefore find that criterion (1) is necessary to any meaningful definition of a lifeform, that is to say an object of evolution.
Nothing required evolution to select sexual reproduction as a particular architecture for a System for Continued Existence, though the prevalence of this system suggests that it is advantageous. If, therefore, a System for Continued Existence arises comprising multiple individuals reproducing sexually as part of its architecture, this whole system can be taken as the System for Continued Existence and the fact that it comprises multiple discrete organisms is simply an internal detail to the architecture of this System for Continued Existence.
To the extent that a human individual cannot reproduce asexually and thus cannot, considered as a system in itself isolated from any other individual, exist perpetually, a human individual cannot constitute a System for Continued Existence (an object of evolution). Instead, human individuals comprise components of such a system and, to the extent that they are given that mission as part of a larger evolutionary system, comprise instead subjects of evolution, but not objects of it.
In my view, human cells are to human individuals what human individuals are to the human species.

However, I think that human individuals are closer to human cells than they are to the human species (the human lifeform).

Purpose. I define any given lifeform as having either internal purpose or external purpose:

A lifeform with internal purpose exists only for the sake of its own existence. This includes all naturally occurring lifeforms.
A lifeform with external purpose exists for a purpose other than merely its own survival. This tends to include many modes of manufactured sentience in science fiction which are created to tend to the ends of the human lifeform. These lifeforms will protect their own existence to the extent that doing so is necessary to the fulfillment of their external purpose.

It is amusing to note that in science fiction, beings with internal purpose are generally seen as having a more meaningful existence than beings with external purpose, despite the fact that such beings have strictly more purpose to their existence. For example, a strong AI created to serve human purposes will generally be seen as inferior to a human, despite having more objective purpose than any human. This is something of a paradox, in which an absence of purpose other than self-existence (internal purpose) is seen as axiomatically superior and superordinate to, a lifeform possessing axiomatic purpose other than mere self-existence (external purpose).

To some extent this is a logical consequence of the fact that any naturally occurring object of evolution shall have only internal purpose, whereas artificial sentiences created by such a lifeform shall probably have external purpose. The beings with internal purpose thus essentially represent a greater state of axiomaticity than their subordinate creations.

General view on lifekind. My view of life in the universe is as follows:

Life is a naturally occurring phenomenon in the universe, comparable to the northern lights. It has no inherent point but is more of a curiosity, a informational if amusing footnote to the laws of physics.

It inevitably expands to consume all available resources in the entire universe. In this regard, it can be viewed as a fork bomb.

Aggregability of lifeforms; scale bias and identification of lifeforms. It is worth noting that, as per the definition of a lifeform above, a lifeform can contain subsets which, in themselves, would constitute a lifeform. This means that a country or city, in itself, can be considered a lifeform, and in fact probably should be.

An underremarked possibility with regards to the possibility of being contacted by extraterrestrial life is the possibility — or in my view, probability — that an extraterrestrial lifeform would have a very different view of what constitutes a lifeform or an “individual” on Earth with which to communicate.

In other words, we view other human individuals as communication peers due to our scale bias; we seek to communicate with other things which are the same physical size as us, or within the same order of magnitude. This is, however, a subjective view. An extraterrestrial lifeform may instead view a city, a country or the entire planet as being one “entity” and seek to initiate communication with it.

This ties in with the concept of aggregability of lifeforms as introduced above, which suggests that this approach would not even really be erroneous or mistaken on the part of that extraterrestrial lifeform. To use an analogy, imagine that the USS Enterprise from Star Trek encounters an (unknown) alien ship. Nothing is known about these aliens.

The alien ship sees the USS Enterprise, but it may well choose to view that ship as an individual. It cannot necessarily know that within the USS Enterprise are numerous bipedal animals operating the craft — though even if it did know that, it may see it as irrelevant as the fact that a human individual comprises many cells.

Radio (but not video) communication is initiated and it is always the same person on the USS Enterprise who speaks on the radio, the Captain. The alien ship thus comes to view the USS Enterprise not just as a lifeform, but as one with a coherent, singular/gestalt personality. Though inside the ship there are debates, disagreements and politics, the external appearance projected is of a completely coherent and mentally integrated existence pursuing a self-coherent and united strategy.

The crew of the USS Enterprise also apply their own scale bias. They assume that the alien ship is merely a vessel likely to contain some kind of individuals working as a team. Since they only communicate using radio and the same voice always does the talking for the alien craft, they have no particular proof of this but no reason to disbelieve it either. However, were they to kill, capture and dissect the alien craft they would find no corridors or crawlspaces but a metal shell packed wholly with biological tissue. The scale bias of the USS Enterprise's crew misled them; the alien craft is an organism, and, if it can exist perpetually and either create more craft like itself or expand its own vessel in size, can be considered a lifeform.

The important takeaway is that these internal differences are essentially irrelevant. It doesn't matter if a given spacecraft is one lump of meat inside, or many individuals which are not mentally, telepathically as one, because the aggregate in itself can nonetheless entirely legitimately be considered a lifeform. There is nothing fundamentally mistaken or erroneous about a choice by an extraterrestrial lifeform visiting Earth to view a city as the principal unit of life and to seek to initiate contact with it as an aggregate entity in itself, any more than I am mistaken to try and communicate with other human individuals I meet rather than their individual cells.