i is also a quaternion. So by this logic we could say complex numbers are made up of quaternions. But we don’t say such things because they wouldn’t be a good mental model of what we want to talk about.

> i is also a quaternion

Yeah, so ?

The fraction 1/2 is a rational and also a real and also a complex numbers and also a quaternion also an octonion ....

We use a number along with the minimal abstraction that is sufficient for our purpose.

i=0+1*i =0+1*(0+1*(0+1*(0+1*(0+1*(0+1*( ...*