Reference::
You sit at the dinner table and share an idea you were thinking about. Lo and behold, others start sharing their perspectives, debating you, and so on. This is a great way to shape your ideas better.
Let's see why.
The act of externalizing your thoughts—even vocally—requires clarifying and completing your ideas, which, similarly to writing, leads to better understanding. What's more, since when you're discussing something you're talking to others (not to yourself like when writing), you must tailor the information to the recipient. Usually, this entails simplifying the information, which often forces you decompose it into its building blocks (PN: The first principles), which usually exposes how much you understand it.
Further, discussing has one advantage to writing—other people's input.
Whereas during writing you're consulting your previous thoughts and notes to make your ideas clearer and more complete. During discussions you're using other people's input for that.
Other people can call out holes in your arguments.
Other people can supplement your ideas.
Related: This can act as adding missing "parts" to any of your incomplete ideas, leading to new lines of thought: PN: Most new ideas are incomplete
Sharing your ideas and trying to persuade others is a great way to learn. You learn most by teaching.
It shouldn't be an either or. I think it's best to combine those two methods. Thinking > Writing > Discussing >
Widen your options trigger
What's more, to fucking ace the learning you can add another thing—doing. When in discussions you're getting other people's input, in doing you're getting the input from reality. Thinking > Writing > Discussing > Doing. And all of these methods update the first one. After each writing, discussion, your thinking gets clearer and more complete.