  Future intelligent autonomous systems (IAS) are inevitably deciding on moral
and legal questions, e.g. in self-driving cars, health care or human-machine
collaboration. As decision processes in most modern sub-symbolic IAS are
hidden, the simple political plea for transparency, accountability and
governance falls short. A sound ecosystem of trust requires ways for IAS to
autonomously justify their actions, that is, to learn giving and taking reasons
for their decisions. Building on social reasoning models in moral psychology
and legal philosophy such an idea of >>Reasonable Machines<< requires novel,
hybrid reasoning tools, ethico-legal ontologies and associated argumentation
technology. Enabling machines to normative communication creates trust and
opens new dimensions of AI application and human-machine interaction.
  Keywords: Trusthworthy and Explainable AI, Ethico-Legal Governors, Social
Reasoning Model, Pluralistic and Expressive Normative Reasoning
