 Perhaps the most important work Berlin did in ‘pure’ philosophy, in the light of his later ideas, concerned ‘logical  translation.’[4]  In his essay of that title (reprinted in 1978b), Berlin criticised the assumption that all statements, to be genuine and meaningful, or to claim correctness, must be capable of being translated into a single, ‘good’ type of proposition, and asserted that the ideal of a single proper type of proposition was illusory and misleading. He identified two different, opposed approaches based on this erroneous assumption. One was the ‘deflationary’ approach, which sought to assimilate all propositions to one true type. Thus, phenomenalism sought to translate all statements into assertions about immediately perceived sense data. The other was the ‘inflationary’ approach, which posited entities corresponding to all statements, thus ‘creating’ or asserting the existence of things that didn’t exist at all. Both of these errors stemmed from a demand for a ‘forcible assimilation’ of all propositions to a single type. Berlin suggested that such a demand was based, not on a true perception of reality, but rather on a psychological need for certainty, uniformity and simplicity, as well as what he termed the ‘Ionian Fallacy’, the assumption that everything is made out of, or can be reduced to or understood in terms of, one and the same substance or  type.[5]