Comment by cubefox

Here is my explanation why language seems to be, while not necessary, so useful for abstract thought: Thinking thoughts with abstract concepts takes up a lot of working memory. We can't hold many of those in mind at once. But if they are expressed in words they take very little memory. So we can have long winding and abstract thoughts because language compresses the parts of the thought complex we are not currently focusing on, so we can hold more of it in short term memory. In effect it increases our thinking cache.