Language is the true nature of thought.

Thought is just modeling the world, nothing more, nothing less. The brain has a fundamental capacity to analyze your environment, deduce patterns, and make predictions. That’s basically its function. So when an animal has a goal to achieve, the brain runs little experiments to try and predict the best course of action based on its existing model of the world. That’s thinking. Animals think, too. If they didn’t, they wouldn’t be able to try anything new in a deliberate way, and the only deviation of their current behavior from past behavior would be random, like in natural selection. But it’s not random, they are quite smart in how they try different things. So they think.

But they don’t have language, so they don’t think in words. We do have language, so when we try and analyze a situation, words pop up in consciousness. Thought is, strictly speaking, only needed when you learn something new or try to solve a problem you didn’t solve before. For example, when you drive a car, you don’t think about it at all, but when you were just learning to drive, you constantly thought about the next thing you would do. Driving behavior was new for you, and it’s not anymore - so you just drive and you can think of something else. Unfortunately this something else will probably be “you”.

You see, what I said before only applies to thought about your environment. Self-referential thought, that is, thinking about yourself, your past, your future, your life, your social status, your successes and failures is a human phenomenon, and its nature comes from ego. It’s expressed as thought in language but underneath it there’s an imaginary entity of a social “you” which cannot be found in physical reality, and is ultimately made up by the mind. Animals don’t have that, which is why in the absence of physical danger they are always happy and content. Humans get lost in it, which is why they are restless in a never-ending pursuit of happiness which never comes. It is possible to get rid of it, and then it becomes possible to execute a familiar behavior like drive a car with no thought whatsoever (a still mind), but words still pop up when you have a problem to solve or learning something new.