Born in England, Johnson emigrated to America in 1801 and had a successful career as a banker. His philosophical interests centred upon language, whose misunderstanding he regarded as responsible for endless confusion and error. In a manner reminiscent of Berkeley he distinguished the ‘sensible’ meaning of terms, tied closely to the experiences to which they refer, from merely ‘verbal’ meaning. The sensible meaning of a sentence is given by what would now be thought of as its verification conditions or assertibility conditions. Johnson’s conviction that we erroneously attribute extra significance to sentences is a forerunner of the logical positivists’ polemic on the same point. Johnson’s principal work was the Treatise on Language (1836). His remark that ‘we can no more exemplify with words that there is a limit to their applicability, than a painter can demonstrate with colours, that there are phenomena that colours cannot delineate’, is a striking anticipation of Wittgenstein’s more famous distinction between what can be shown and what can be said.