Kant: How is Pure Mathematics Possible?

"If two things are quite equal in all respects as much as can be ascertained by all means possible, quantitatively and qualitatively, it must follow, that the one can in all cases and under all circumstances replace the other, and this substitution would not occasion the least perceptible difference." (section 13)

Here Kant is saying that if two things are equal in every aspect that one could substitute one for the other and nothing would change. It is very interesting and slightly confusing that Kant can put such an obvious thing into such ridiculous phrases. Although this is correct in our minds I do think that there is a way around everything. And even though something appears to be equal it may not be.