Yes. Smalltalk has the ifTrue: and ifFalse: methods on the Boolean object.
x > y ifTrue: [ Transcript show: 'Truthy' ]
So it is using polymorphism as the main mechanism. The True object implements ifTrue: by evaluating the block argument and implements ifFalse: by doing nothing. The False object does the opposite.
Comments
It's easy - use switch/case statements!
But seriously, isn't it true that Smalltalk doesn't have if statements?
Yes. Smalltalk has the ifTrue: and ifFalse: methods on the Boolean object.
So it is using polymorphism as the main mechanism. The True object implements ifTrue: by evaluating the block argument and implements ifFalse: by doing nothing. The False object does the opposite.