one should see how we came to the modern understanding of a given problem (" ... how we know what we know"). The theory of "nonclassical" ions offers an explanation of many unique chemical, stereochemical and kinetic peculiarities of bicyclic compounds. It has expanded our knowledge on chemical bonds in carbocations by introducing electron-deficient bonds (as in boron hydrides). It has accounted for many rearrangements of stable cations. As a "side" result our knowledge has been extended about ionization processes in a solution, as well as about stereochemical methods. 2 Main Terms of Nonclassical Carbocations In 1939 Hevell, Salas and Wilson 23) assumed an intermediate, "bridge" ion 2 to be formed when camphene hydrochloride 1 is rearranged into isobornyl chloride 3. This happened 17 years after Meerwein first postulated the intermediate formation of "carbonium" ions in chemical reactions.