Traditionally, philosophers looked for philosophical systems. By definition, systems are (sets of) theories that include answers to all important philosophical questions, or at least methods for finding them. Contrary to received opinion, it is not advisable to offer a philosophical system: it amounts to the offer to relinquish all moral autonomy. Moreover, no one ever proposed a philosophical system proper. All known theories have huge gaps in them. Traditionally philosophers are hostile to philosophies that are frankly open, thereby expressing — knowingly or not — preference for a closed philosophy as a preference for a closed society. This causes much frustration. Openness is essential to modern pluralist democratic society — and to science too.