He presented sin and vices as contraries of virtues. Although Aristotle argues that circular motions are not contraries, they could still lead to collisions. Amongst walls that are impermeable to matter, diathermal and adiabatic walls are contraries. Realist and constructivist theories are normally taken to be contraries. "Oh, to vex me, contraries meet as one" are first found in 1620. Afterwards, Plant began an investigation on the contraries and clowns of the Plains Indians. Opposing pairs of these are joined by a bar labeled "contraries" (earth-air, fire-water). The Contraries of the Plains Indians were unique and historically unprecedented. By contraries, "g" sometimes becomes "k" and "b" sometimes becomes "p". He can swiftly interpret contraries by references to differences in situation.