I, like many other people, have discovered that it is almost impossible to think seriously without writing. Writing clarifies and sharpens your thoughts in a way that is superior to merely articulating them in a conversation. It allows you to look at your ideas more objectively, almost as if they were from another person. You can then examine them and think about if what you have written down is really true.
However, more often than discovering that your ideas are wrong, you will discover something different: that you do not know what you think. Sure, you have some vague idea, and you believe that there is a chain of reasoning that leads to a certain conclusion. But what you will discover is that this chain of reasoning is mostly not existent. At best, it has many holes and maybe leads not where you think it does. This discovery is, of course, very unpleasant and sometimes even painful. In a sense, you have lied to yourself by thinking you have thought through this specific topic when, in reality, you have only copied the opinion of someone else.
This process requires an immense amount of honesty because nobody likes to feel stupid. Either you do not know what you think, in which case you feel stupid. Or it turns out that what you believed to be your opinion does not really make sense, is logically inconsistent, and mostly copied from someone else, in which case you feel stupid as well. However, the reward for all this exhausting work is clarity and simplicity. You now possess a chain of reasoning where you have looked as carefully as you can for holes and problems. The next step is to let others examine your reasoning—publishing.