Just a note:
In Buddhism, there is a difference between a Reality -- a
Dharma (a phenomena that is experientially real),
and a concept.
For example, a Universe 'out there' is a concept. For
example, Male and Female is a concept. It is not an
experiential reality. It is not a Dharma. Dharma is simply
experiential reality, and the nature of experiential reality is
Luminous and Empty. While there is the quality of awareness
(luminosity), it is at the same time empty of inherent existence,
ungraspable.
The Buddha taught that the ALL is only 5 Skhandas
(form, feeling, perception, volition, consciousness) and
18 Dhatus (6 sense organs, 6 sense objects and 6 sense
consciousness).
That means All There Is, i.e. our Entirety of Experiential
Reality is only the 5 skhandas (prior to enlightenment)
and the 18 dhatus, and there is nothing apart from that. That is,
the All in Buddhism is only the experiential reality -- the All is
really just our awareness in its differing conditions. Note
also, that Buddhism does not teach an Atman, a Soul or a higher or
permanent reality of any sort apart from the 5 skhandas and 18
dhatus. Instead, Buddha Nature is refering to the nature of all of
our experiential reality (i.e 18 dhatus) being
luminous-emptiness inseparable.
Anything apart from that would be a Concept, not a Reality
(dharma).
When the Buddha taught that All Dharma is
Anicca, Dukkham, and Anatta, he is refering to our Experiential
reality as being Impermanent, Suffering and No-self.
He's not talking about concepts such as Universe as being
impermanent. Of course he do talk about such concepts, and also to
remind ourselves that life is impermanent and the time of death is
uncertain, but when he is teaching the Dharma
and the practices, he is not refering to concepts but
refering to experiential reality -- i.e. our Awareness.
So when we are contemplating impermanence, which is a form of
Vipassana (insight meditation) we contemplate at an
experiential level. That is by direct experience without further
labeling and symbols, we experience our 5 skhandas as being
impermanent, non static and everchanging. Also, as suffering, as
non-self. As empty.