You are not the body.

This can be demonstrated in myriad ways. Here’s but one:

C1: I am the body.

C2: I own the body. (The body belongs to me.)

Note that there is an obvious logical contradiction between C1 and C2: C1 and C2 can’t be true at one and the same time. I can’t, at one and the same time, both be the house and be the owner of the house. The same is true here.

Therefore, the first modification that we commonly make: sometimes I believe that I am the body while at other times I believe that I own the body. Now there is no contradiction.

But consider C3:

C3: I have never had an experience of being different from myself.

C3 is true–though the intuition will need to be clarified in your own experience.

Since C3 is true, neither (a) C1 on its own nor (b) C2 on its own nor (c) “sometimes” C1 and “sometimes” C2 can be true.

I can’t be the body because the body changes while I do not (C3).

I can’t be the owner of the body because, again, the body changes while I do not.

And I can’t change from C1 into C2 because I’m never different from myself.

It’s not a logical inference to say that what I am is not the body. It’s self-evidently clear in my own experience.