"Cogito ergo sum", or "I think, therefore I am". Descartes wrote this famous line. This is the start of philosophy -- being able to think. We think that we think, therefore we exist. Everything that we do, we go through many thought processes, emotion, complex decision making abilities and so on. The result is an action. What would it be like if we are not able to think? Is this thinking ability the only thing that we have that relates to our existence?
The thinking mind in Buddhism didn't come to existence because there is a person who is able to think. If you exist because you are able to think, what comes before you are thinking? Thought processes itself form because of interactions with the environment. The thinking mind is in fact the function of the Buddha mind. However, we always want to grap onto something we can see. For example, because we cannot see supernatural beings, we negate their existence. Before microscopes were invented, people don't believe in microorganisms because they cannot see them. Because we are always grabbing onto forms, we grab onto our thinking minds, thinking that it is us. Therefore "I think, I am".
If you contemplate closely, we can realize that the thinking mind is not us. We can "separate" ourselves from our thinking mind. By separation here, I do not mean that we deny the existence of the thinking mind. Know that it follows you, and will come and go, like a shadow. When the sun is shining bright, you can see your shadow, but you won't be surprised of the black figure following you around. When light disappears, so does your shadow. Do not push your thinking mind away. It will be like trying to cut your shadow away from you in the sun.
What should we do then? Make friends with your thinking mind. Understand how does the thinking mind come about? Where does it come from? How does it look like? Where does it go? It should be effortless. If you are using a lot of effort, you will strain yourself. But it does not mean you listen to your thinking mind, or become lazy. Always be present. Always watch the thinking mind. The thinking mind is just the waves of the ocean. Without the ocean, waves cannot appear. When the ocean is there, waves will appear when there is wind. The thinking mind is like that. The ocean just let the waves go by. The ocean can also make water sprouts, tsunami, and other tidal waves. It depends on the weather conditions at that time. The ocean does not swallow the waves, the ocean just let it be, because if it can arise, it can go away. The thinking mind is just like the water sprouts, tsunami, tidal waves. They come and go. They do not stay. Therefore it is like a shadow. Sometimes, it is there, sometimes it is not. We just have to watch and see where it comes and goes.
When we contemplate on the mind, we don't use logic to think about what the mind is, or where it is. Do not use logic. That is already grasping onto forms. Cultivation is not gathering of knowledge. Contemplate. Observe. Watch. Be aware. So which mind should we contemplate on? If "I think, therefore I am", then what comes before "I think"? That is what we should contemplate on.