For those of the tradition of Marxian thought to which I subscribe, the term "subject" in general --
as a "genos" -- refers to a name rightly [or aptly-descriptively]
placed into the subject position of a well-formed, e.g., Indo-European,
sentence, i.e., that is placed into the action-initiating, or 'agental',
position of that sentence.
Sometimes, that "subject" will be the name of a human person, or of a
human collectivity, and then, in that case, we will be dealing with
specifically human "subject-ivity", and with the "dialectic of human Nature" "species" of the dialectics of Nature.
If that sentence has the same name in both the subject and the object
positions, and if that sentence also has a verb which names the essential activity of that subject-object, i.e., that activity which expresses the very nature or character
of that subject/object, then we have a "self-reflexive" sentence,
describing the "self-change", or "autokinesis", of that
subject-verb-object, and we also have a "subject-verb-object identical"
This kind of sentence, describing a "self-duality", or "intra-duality"
between the "subject-aspect", or "agent aspect", and the "object
aspect", or "recipient of action", aspect, of the given
"subject-verb-object-identical" sub-whole described by the sentence --
the existential [NOT propositional] "internal contradiction", or
"immanent contradiction", or "self-contradiction", that drives the
self-induced development of that "EVent-ity" -- is especially
well-formed for describing dialectical processes.
For example, the sentence --
"Humanity -- i.e., the complex unity of the "human phenome/human genome"
-- when it is self-observed historically, is seen to have
net-expandedly reproduced itself, as such, in both quantitative and
qualitative senses of the term "net expansion"."
-- is such a sentence.
But the following sentence is also such a sentence --
"The star called the sun continually self-gravitationally implodes itself, and, concurrently, also continually thermo-nuclearly explodes itself from
its core, producing a billions-of-years-prolonged, but still transient,
"dynamically quasi-stable quasi-stasis" in the stellar main sequence,
until its core Hydrogen "fuel" is fully-depleted / converted into Helium
"ash", i.e., until it has "polluted" itself with Helium "waste",
causing its inner fusion fire to go out, so that it begins again to
implode / contract / self-densify its core even further, eventually
crossing the density threshold whereafter that Helium "ash", that
"waste", that "entropy", turns into a new "free energy", a new
"resource", a new "fuel"."
The latter sentence, which, although its subject and object positions
are occupied by the name of a natural object / "event-entity" which is
NOT a HUMAN-natural object, not a HUMAN subject, nevertheless describes a
causal agency or AGENT, and thus a subject in our
generalized sense; a generator of actions upon the rest of the universe
[within its light-cone, or via "quantum entanglement" even outside of
its "light-cone", however much or little attenuated by distance the
impact of these actions may be], AND of actions back upon itself;
actions that change this subject-verb-object, and which ultimately bring
about its no-longer-existence as-such, as a star.
This latter "self-re-flex-ive", "self-change"-describing sentence also
describes a dialectic of nature, but a dialectic of EXTRA-human nature,
or of "EXO-human Nature", and of largely PRE-human Nature, rather than
describing a dialectical process of/within human nature -- within the
human zone of nature, e.g., within that "complex unity" known as Earth's noosphere/biosphere.
Thus, in this sense, not all "subjects" are human subjects, and not all
"subject-ness", or "subject-ivity", or "subject-hood" is human, or
For more about this view, see F.E.D.'s "Introductory Letter" --
-- [see especially the section entitled "The Secret of the Historical Dialectic"].