People might discuss what exists based on the agreement that something exists.
Then Decarte said "i think therefore i am". This is an ambiguous statement because the existence of thinking does not necessarily mean that the object of thought is as real as the thinking itself and repudiates thinking. It can be said that the ideation of 'i am' there is included in the reality of thinking, it is a thusness and a variety of thinking.
Take this statement 'I think about spiderman, therefore spiderman is real'. Well it is and it isn't, it isn't real as the thinking is real because it does not repudiate thinking but it is real as it is that what i think about.
What would be repudiative to thinking? Well in example it can be agreed that seeing is real and it repudiates thinking. It is something that is as real as thinking is real and is real in the same context. There can be seeing without thinking and they are both real in the same sense.
If i said that spiderman is as real as superman, this would be similar. They are both real and repudiate eachother in that imaginary world of superheroes, in that context we can delineate a distinction and separate them. There can be spiderman without superman.
We can delineate a distiction between thinking and that which we think about but we can not separate the object of thought from thinking, there can be no thinking about superman without thinking. What is meant is that we can only separate that which thinks from the object of thought by changing the object of thought, think about something else but an object of thought is something included in thinking itself.
We differentiate between that which thinks and the object of thinking when analyzing the constituents of the reality of 'thinking'.
There can be hearing without discursive thought, likewise smell, taste, seeing & sensations, these are affirmed to exist in the same context and are repudiative of eachother.
The Buddhas say that nothing repudiates the allness of nose & aromas, the eye & the forms, the ear & sounds, the tongue & tastes, the body & bodily sensations, the intellect & ideas.
They don't say that the eye isn't real, the eye is something among everything.
The ideation of spiderman is also something among everything and spiderman is something among everything. Spiderman is something i think about and it is something particular in the imaginary world of superheroes. Doesn't mean that i should go looking for a spiderman in the backyard and if i was to go looking then i would've been doing so due to grasping with wrong view.
Being classed as something among everything doesn't make something as real as everything else, it only makes it as real as that which it repudiates.
It is said that everything is thought of as conditioned element and the thought of the conditioned is repudiated by the thought of an unmade element. This unmade element is not a class of somethings unlike that which is spoken of as everything and the unmade isn't a something among everything even tho the thinking & speaking of it is something among everything.
It is not an everything for it is a single element, not a class of elements unlike ie the element of 'thinking' is a class of that which thinks and that which is thought about or how everything is a class of somethings.
Not being a class[ification] of somethings, it isn't a class or an aggregate of somethings, nor is it being classed as something among everything, it therefore does not contradict the Sabbe Sutta wherein it is said:
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."
It doesn't contradict it because it is not another everything nor a something among everything by definition but it is that which isn't included in the allness of the all.
"'Having directly known the all as the all, and having directly known the extent of what has not been experienced through the allness of the all, I wasn't the all, I wasn't in the all, I wasn't coming forth from the all, I wasn't "The all is mine." I didn't affirm the all.
One should note that intellect in the sabbe sutta can be substituted for mind or consciousness
what's called 'mind,' 'intellect,' or 'consciousness,' the uninstructed run-of-the-mill person is unable to grow disenchanted with it, unable to grow dispassionate toward it, unable to gain release from it.
Then it can by inference be spoken of as is that which knows & cognizes the ideas and also as that which cognizes the forms visible by the eye and knows eye as the eye.
Therefore one can see that
When an object enters ‘the door of the eye’ or any of the other 5 senses, it enters also the door of ideation; ‘the door of the eye’ is included as a delineation of the spheres of the mind-base, included in what is called ‘mind-base’; it is mind-made. (for reference; M. i. 295 (see Caroline A.F, Rhys Davis, first translation of Dhammasanghani Psychological ethics))
Unfortunately i can't find a better reference explaining this and didn't take note of where i found the above excerpt but i am 100% sure this in the theravadin texts and that there are better & more authoritative sources, i just didn't take note and didn't save what i've come across when studying abhidhamma and their comy.
"Feeling, perception, & consciousness are conjoined, friend, not disjoined. It is not possible, having separated them one from another, to delineate the difference among them. For what one feels, that one perceives. What one perceives, that one cognizes. Therefore these qualities are conjoined, not disjoined, and it is not possible, having separated them one from another, to delineate the difference among them."
So this is how one infers the 6 classes of ideation, feeling & perception.
Furthermore what exists that has come into being, what has come into being is made and made is another word for sankhara or creation and it is therefore also conjoined with perception, feeling & consciousness.
That leaves only the class or aggregate of form which is basically a subset of ideation thusness pertaining to the 5 faculties of seeing, hearing, smelling, tasting & sensing with the body.
This subset of ideation describes the thusness of ideation and does not repudiate ideation, it isn't discursive thought or a mental act of adding two numbers together; but it is a mental act of conception & perception of particular elements namely the eye & visible forms, nose & aromas, ear & sounds, tongue & flavors, body & bodily sensations, these color the ideation as that based on the five faculties by which one experiences agreeable & disagreeable things.
This is how one infers the 5 aggregates where 4 aggregates are conjoined from the sutta and how there can be arupa jhana.