he found that euclid's fifth postulate is equivalent to the one currently named "wallis postulate" after him. this postulate states that "on a given finite straight line it is always possible to construct a triangle similar to a given triangle". this result was encompassed in a trend trying to deduce euclid's fifth from the other four postulates which today is known to be impossible. unlike other authors, he realised that the unbounded growth of a triangle was not guaranteed by the four first postulates.