How can I know the things my brain interpret are real? How can I know cognition doesn't filter information out? How can I know that everything I believe is not projection or mirroring of what I am?

  • What hypotheses have you formed? What has your research uncovered so far?
    – Joseph Weissman
    Commented Dec 23, 2016 at 16:13
  • Two main lines of research: 1) Daniel Kahneman shows how our brain categorizes truth with his System1 and System2 model. One can conclude that internal truth can be easily manipulated. 2) (this is me) our cognition mainly target outside information that has an internal identification, we simply don't see what we have not inside. This means we are actually experiencing ourselves through external triggers, all the time. Leading to the the conclusion that what feels real to me, doesn't mean is real to anybody else. Commented Dec 23, 2016 at 16:23
  • This is one basic thread of idealism in an anti-realist form. Consider looking up questions on those topics? At root, this might be a duplicate of philosophy.stackexchange.com/q/38710/9166
    – user9166
    Commented Dec 23, 2016 at 17:55
  • Kahnaman does not demonstrate this. What he presents is a way of looking at things (a model) which he solicits agreement with. There is a huge epistemic difference between what is true and what is "true to..." [to you; me; us or them]. There is no such thing as "internal truth" and there is an epistemic limitation to self-knowledge, i.e. it cannot be verified by others, e.g. "I feel glad" or "this feels like ... to me." Read J. L. Austin's "Sense and Sensibilia" if you feel "led to a conclusion" about degenerate "internal identifiers."
    – MmmHmm
    Commented Dec 23, 2016 at 18:46
  • You can because you do. Knowledge is not supposed to be something immune to objections and doubts, it is something you go on despite them.
    – Conifold
    Commented Dec 24, 2016 at 6:03

3 Answers 3


If you want to remain skeptical of the world and your observations of it, there is nothing which will convince you otherwise, however, I suggest at the very least you distinguish intuition from projection. Also consider distinguishing illuminating appeals to skepticism from unilluminating appeals to skepticism(those which lead to knowledge or the means to obtain further knowledge, and those which induce a resigned ignorance).

As for your questions, consider that "we" don't do "cognition" the individual does. Consider that certainty and confidence are only a mood. Consider that you did not invent the language you use. Consider as you read this that you did not write it. Of course observation and knowledge of the world is imperfect, incomplete and down right degenerate, however, in spite of this we build bridges, skyscrapers, send men to the moon and back and replace human hearts with imperfect, non-absolute knowledge of the world (what is, the case, states of affairs).

You could read DesCartes Meditations and rest assured that everything can be doubted except that you are thinking - even when you imagine thinking to be the passing from one imponderable analogy to the next. You could read Searle's "Intentionality" and ponder how consciousness is directed at things in the world. If you are tempted to solipsism, consider that first person subjective solipsism is irrefutable in the same way a child can say "no" to everything; consider as well that 2nd person subjective solipsism is immediately refuted by any other first-person subjectivity.

Can we trust each others cognition? Yes. Again: we have the language we use which we did not invent to remind us every time we try and communicate with anyone else.


If knowledge is possible, most of it would have to be contextual and defeasible. If so, we're open to correction, for we are not immune from error. A good heuristic to start out with is falsificationism; we can falsify at least some empirical propositions, and those that have been falsified we know we can rule out as being true, especially when they represent empirical hypotheses given certain conditions.


Everything you know is subjective. You can share subjectivities with others (some say that objectivity is just shared subjectivity, that's called intersubjectivity) , but that knowledge is not the same as reality.

Your knowledge about reality is a map. My knowledge, too. Our maps can be similar. But reality is the terrain. Both of us can follow a road that ends on a bridge that has just collapsed. Neither you nor me will be able to know that the route is now lethal. And we may die.

So, we don't have any other option than trust in our subjectivity. And die finding errors on our maps so the people that comes in the future avoid making our mistakes.

In simple words, you can't know if your knowledge is real, but you need it, it is the only one you have, and when you use it, you can die.

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