Book excerpt: is both a player and a spectator, is explained here illuminatingly. With regard to logical ambiguities and paradoxes, which may show up in all these topics, he, like Locker, is of the opinion that, philosophically speaking all apory of a lower level have to be accepted an a higher level of thinking. After the above expositions of a more general purport we turn now to two contributions which are particularly focused on Bohr's concept of complementarity. First is the article of Hilgevoord who briefly and non-technically describes a short curriculum vitae of the concept beginning with Planck through Bohr to Heisenberg and Schrodinger. Included in this short story, of course, is the famous wave-particle duality and the paradox inherent in it many physicists are still saddled with. How this paradox was solved is explained here simply and clearly: first, generally by quantum mechanics where the disturbance theory of measurement was supposed to be of some relevance, and secondly, where this theory is further refmed leading to Bohr's conclusion of the essential unsolvability, and accordingly the completeness, of the statistical element of quantum mechanics. The reading of this short article may arouse questions and surmises whether complementarity has been ruminated by Bohr to tame the law of excluded middle dividing the well-defined content of position measurement from that of momentum measurement, just to mention one. Whatever it may be the idea of complementarity betrays the perplexity of the observing system in dealing with nature's complexity.