Maybe we just don't see an idea because it is not for us to see in our purpose for life. If we are all individuals each here with a different purpose, I think it may just be possible in order to fullfill our purpose we don't grasp all ideas.
And to disagree with a theory or in conversation, we grasp the concept of the idea behind whats being said, and therefore have the ability to either agree or disagree with it.
Just phillisophically saying.

Vincent, I totally agree that words do not have the same meanings to everyone.

Thomas Kuhn makes a big deal of this phenomenon with respect to the history of science. The fact the same word can have different meanings within different paradigms (like the meaning of "mass" in classical mechanics vs. the meaning of "mass" in relativistic physics) is one of the factors that makes straight-forward comparison between theroies problematic.

On network theories of meaning, a word gets its meaning in part from the other words we associate with it. And since everybody's associative net is a little different...

Wittgenstein had a lot to say on this matter. He suggests that what a person says, their words, gestures and expression are uttered within a context a ‘language game,’ and a culture, or ‘form of life.’ These utterances have no objective meaning, only a meaning to someone in a context – there are no meta-languages. Our internal images, mental states or propositions are interpreted through a shared set of signs and concepts. These signs or words have a shared/agreed correspondence or relevance in response to certain things, this is what makes communication possible. It is important that we agree nearly all the time on what words are referring to – otherwise it would not entail communication. There is regularity in the use of concepts and collusion in the utilization and application of language. So for Wittgenstein ‘forms of life’ or context and ‘language games’ are interdependent – different concepts are more useful and pertinent in different contexts. So understanding others involves empathy which involves a similarity of experience or life world and language. When we learn to express pain as a child it becomes associated with, it corresponds to and inseparable from, a shared set of words and gestures that are learnt and become inextricably associated as signs of pain. “There are not meanings going through my mind in addition to the verbal expressions; the language is itself the vehicle of thought”. These ‘rules’ or ‘regularities’ of expression must be shared there must be an agreement through conditioning and education that is essential for communication to be communication. I do not know their pain by hearing them utter as such, but I do know, through sharing the same life world as this other person, that he is in pain which makes me respond accordingly – the purpose of these signs is to communicate this internal state.
However, Wittgenstein points out that there is much confusion in the use of language, that language is not immutable – meanings and the use of terms can change. Moreover, he notes that many philosophical problems are “[m]isunderstandings concerning the use of words, caused, among other things, by certain analogies between the forms of expression in different regions of language.” For the later Wittgenstein, many philosophical conundrums are dissolved by having a clear understanding of the inner workings of the language used, related to its pertinent context, and arranging the information and knowledge accessible to us in different patterns perspectives. So, certain philosophical propositions are simply a misuse of language out of its context and the limits of its meaning, often not actually problems at all when framed differently. So, “Language sets everyone the same traps; it is an immense network of easily accessible wrong turnings.”
Furthermore, for Wittgenstein there are also limits to descriptions through language, the inexpressible that lies beyond propositional sense. But this does not stop language from conveying or communicating as this is its primary objective, if not, then it is not a language game at all. There are also blurred or fuzzy concepts that are accepted in ordinary language which do not have an exactness, conceptual similarities that referred to concepts that have a ‘family resemblance’ or have common features. These ambiguous notions are helpful tools that refer to things that would otherwise resist being nailed down precisely – which, more to the point, would thereby no longer be helpful. This is not miscommunication but a tool to communicate things that would otherwise defy the logical limits of language – we nonetheless have a shared or agreed acceptance of these notions that fall under a ‘family resemblance’ an ambiguously abstracted similarity that narrows down what we are referring to which makes it possible to refer to such things in communication. Ambiguity in language is not a problem all the time, rather a necessary requirement for us to refer to things that would otherwise be outside or transcend the parameters of language without such fuzziness.