Notice the language we use to describe driving and car accidents. When I drive, I can feel every bump in the road. I did not roll through that stop sign. I get anxious whenever someone tailgates me. I was distracted and went off the road. Suddenly, there was a tree in front of me and I hit it. I was rear-ended by a guy on his cell phone.
When people talk about driving, the car is often left out of the conversation. Admittedly, it is easier to say "I was rear-ended by a guy on his cell phone" than to say "The car I was driving was rear-ended by a car being driven by a guy on his cell phone." But the simpler statement also describes what it feels like so much better as well. This describes the experience because when I drive my car becomes an extension of my physical self. I become my car.
Perception is one component of how my car (and my toothbrush) becomes part of me. Anything that moves with me seems to be an extension of my self. My clothes move with me and if you touch the shirt on my shoulder, I feel that you have touched me. When I drive, my car moves with me and if your car hits mine, then I feel that you hit me. Moving together isn't the whole story, however.
Manipulating an object is also crucial for extending my self into the object because being a passenger is different from being the driver. When I am a passenger, the car and I move together and I can feel the road through the car. In that way, I begin to feel that the car is an extension of my physical self. The effect is more dramatic, however, when I am the driver. When I drive, I control how the car moves. I see the pothole, anticipate the bump, and feel it much the way I do when walking over a rough path.
Using tools of any sort allows me to extend my physical self into the tool and perceive the world through that tool. When I play tennis, I hit the ball with my racket. I can feel the ball when I hit it and tell if I hit it well or, more often, poorly. When I mix pancake batter with my whisk, I can feel how thick the batter is and decide if I should add more buttermilk. When I brush my teeth with my toothbrush, I can feel my teeth, gums, and tongue. When I poke something with a stick, I can tell a lot about the quality of that object. Is it hard, soft, sticky, or slick? I feel through these tools, extend my self into the tools, and in that way I have become the tool.
If you want to test the power of this idea, try the following: Poke a child with a stick and play the linguistic game. "Stop poking me," says the child. "I didn't poke you, the stick poked you," you respond. Good luck with that argument. The child knows that you not only hold the stick and control it, but in some crucial fashion the stick is an extension of you.
William James, back in 1890, described another fashion in which I am my car (and my toothbrush). He argued that part of a person's self concept includes anything that the individual claims as "mine". Thus my car is part of how I define my self. For me, my VW Passat station-wagon is part of how I think of my self, whether or not I am driving it at this moment. I jokingly refer to it as my daddy sports-wagon. I am comfortable with that as part of my self but I also look forward to driving more fun cars again. (My wife refuses to think of the wagon as hers and does not define her self by that car.) My sense of self is extended into a great variety of objects and, as James noted, I feel violated if someone attacks or breaks anything I think of as mine.
Thus I am my car (and my toothbrush). When I drive, my car moves with me. When I drive (or brush my teeth), I can experience the world through the tool I control. In addition, I consider these objects as mine, so please don't wreck my car (or use my toothbrush).