I saw @HEMSING's post about sheet music and, as he said, the argument about being able to read or not being able to read sheet music has a great potential as a topic of discussion.
I have always found this topic interesting because it is a topic that touches me personally, being a musician who cannot read music and who has never studied music theory before (until one month ago when i actually started studying music theory from scratch).
But I have been composing music for a year now and, not to be presumptuous, but I seem to have made good music, at least I have been told so ahahah. And this despite my lack of knowledge of music theory.
I think I managed to do this because I am someone who listens to a lot of music, but really a lot, plus I also have a good ear, not perfect but good. So I can recognize when something is wrong just by listening. Listening to a lot of music helps me to have more paths to follow, more ideas to draw inspiration from, if you know what I mean. But the lack of knowledge of music theory prevents me from increasing my possibilities, it limits me. This is why when I compose a song, I very often get stuck because I don't know how to continue.
So, my thoughts are, as most of the people say, knowing music theory or being able to read sheet music is not necessary to be a musician, but it certainly helps to expand our "musical horizons", and it certainly helps to communicate better between us, as music is a language full-fledged, and if I don't know it I will surely have difficulty in talking about music theory with other musicians.
I'd love to hear from you, what your thoughts are about this, and if you can or cannot read music. I am really curious!