Circulation of concepts Abstract A major obstacle to chemistry being a deductive science is that its core concepts very often are defined in circular manner: it is impossible to explain what an acid is without reference to the complementary concept of a base. There are many such dual pairs among the core concepts of chemistry. Such circulation of concepts, rather than an infirmity chemistry is beset with, is seen as a source of vitality and dynamism. Read more...   Playing with molecular models Abstract Any serious study of molecular models has to mention play as a component essential to their use. A research chemist will use them not unlike a young child playing with a toy: exploring their features, trying out their resilience, probing their innards, tinkering, day-dreaming, and finding out in those ways new avenues for adventures of the mind and in the laboratory. Reasons for such assimilation of a molecular model to a toy are given and assessed critically. Read more...