If you're speculating on the nature of the universe or the nature of existence, then the Buddha considered this a futile exercise of intellectual gymnastics that leads to madness in the Acintita Sutta:
"Conjecture about [the origin, etc., of] the world is an
unconjecturable that is not to be conjectured about, that would bring
madness & vexation to anyone who conjectured about it.
The Buddha only concerned himself with suffering, the cause of suffering, the cessation of suffering and the way to end suffering.
In the Parable of the Poisoned Arrow, he taught that a man struck with a poisoned arrow should find a way to remove the arrow and heal himself, rather than investigate who shot the arrow, and what is the arrow made of, and what does the arrow cost, and at what speed was it shot etc.
Of course, from the perspective of the individual, we may ask whether there is a self (i.e. an intrinsic unconditioned reality for a person) or not, and this is indeed related to the path to the end of suffering.
And the answer is clear from the Vina Sutta that the self is a mere mental idea (supported also by Snp 4.14), conjured by the five aggregates of form, feeling, perception, consciousness and mental formations, according to the process of dependent origination:
"Suppose there were a king or king's minister who had never heard the
sound of a lute before. He might hear the sound of a lute and say,
'What, my good men, is that sound — so delightful, so tantalizing, so
intoxicating, so ravishing, so enthralling?' They would say, 'That,
sire, is called a lute, whose sound is so delightful, so tantalizing,
so intoxicating, so ravishing, so enthralling.' Then he would say, 'Go
& fetch me that lute.' They would fetch the lute and say, 'Here, sire,
is the lute whose sound is so delightful, so tantalizing, so
intoxicating, so ravishing, so enthralling.' He would say, 'Enough of
your lute. Fetch me just the sound.' Then they would say, 'This lute,
sire, is made of numerous components, a great many components. It's
through the activity of numerous components that it sounds: that is,
in dependence on the body, the skin, the neck, the frame, the strings,
the bridge, and the appropriate human effort. Thus it is that this
lute — made of numerous components, a great many components — sounds
through the activity of numerous components.'
"Then the king would split the lute into ten pieces, a hundred pieces.
Having split the lute into ten pieces, a hundred pieces, he would
shave it to splinters. Having shaved it to splinters, he would burn it
in a fire. Having burned it in a fire, he would reduce it to ashes.
Having reduced it to ashes, he would winnow it before a high wind or
let it be washed away by a swift-flowing stream. He would then say, 'A
sorry thing, this lute — whatever a lute may be — by which people have
been so thoroughly tricked & deceived.'
"In the same way, a monk investigates form, however far form may go.
He investigates feeling... perception... fabrications...
consciousness, however far consciousness may go. As he is
investigating form... feeling... perception... fabrications...
consciousness, however far consciousness may go, any thoughts of 'me'
or 'mine' or 'I am' do not occur to him."
Then you may say consciousness is intrinsic and unconditioned, but even this is rubbished by the Buddha in MN 38, as he proves beyond any doubt that consciousness is conditioned upon the sensory media:
“Bhikkhus, consciousness is reckoned by the particular condition
dependent upon which it arises. When consciousness arises dependent on
the eye and forms, it is reckoned as eye-consciousness; when
consciousness arises dependent on the ear and sounds, it is reckoned
as ear-consciousness; when consciousness arises dependent on the nose
and odours, it is reckoned as nose-consciousness; when consciousness
arises dependent on the tongue and flavours, it is reckoned as
tongue-consciousness; when consciousness arises dependent on the body
and tangibles, it is reckoned as body-consciousness; when
consciousness arises dependent on the mind and mind-objects, it is
reckoned as mind-consciousness. Just as fire is reckoned by the
particular condition dependent on which it burns—when fire burns
dependent on logs, it is reckoned as a log fire; when fire burns
dependent on faggots, it is reckoned as a faggot fire; when fire burns
dependent on grass, it is reckoned as a grass fire; when fire burns
dependent on cowdung, it is reckoned as a cowdung fire; when fire
burns dependent on chaff, it is reckoned as a chaff fire; when fire
burns dependent on rubbish, it is reckoned as a rubbish fire—so too,
consciousness is reckoned by the particular condition dependent on
which it arises. When consciousness arises dependent on the eye and
forms, it is reckoned as eye-consciousness…when consciousness arises
dependent on the mind and mind-objects, it is reckoned as
The Buddha also taught in the Sabba Sutta, not to imagine realities beyond the six sensory media:
The Blessed One said, "What is the All? Simply the eye & forms, ear &
sounds, nose & aromas, tongue & flavors, body & tactile sensations,
intellect & ideas. This, monks, is called the All. Anyone who
would say, 'Repudiating this All, I will describe another,' if
questioned on what exactly might be the grounds for his statement,
would be unable to explain, and furthermore, would be put to grief.
Why? Because it lies beyond range."
The concept of an intrinsic unconditioned reality is a mere philosophical conjecture and intellectual gymnastics, based on the false view of the self, no different from creationists trying to defend creationism against evolution using rhetorics.
The Buddha's teachings are grounded on his empirical realization of the four noble truths and the three marks of existence, and even today, these can be empirically verified through the Noble Eightfold Path.