That Dispensationalism is a False Doctrine

Define 'Polisoteriology' as 'two or more ways of salvation'.

The argument stated:

(1) Dispensationalism implies Polisoteriology.

(2) But then, there is only one way of salvation.

(3) Therefore, Dispensationalism is false.

The argument defended from the impossibility of contrary premises:

(1a) If (1) is not the case, then there are no such things as several 'Dispensationalist' dispensations. Therefore, (4a) Dispensationalism would be false anyway. For, then, its core argument would be dismissed.

(2a) If (2) is not the case, then (5) Christianity as revealed in the Bible would be false and therefore (4b) Dispensationalism, would also be false. For Dispensationalism claims to be a Christian doctrine.

(3a) Therefore, Dispensationalism is false.