This book constitutes extended, revised, and selected papers from the 12th International Symposium on Artificial Intelligence supported by the Japanese Society for Artificial Intelligence, JSAI-isAI 2020. Organized in the Tokyo Institute of Technology, it was held virtually due to COVID-19 pandemic. The 19 full papers were carefully selected from 50 submissions and present two workshops: Logic and Engineering of Natural Language Semantics (LENLS 2020) focus on the formal and theoretical aspects of natural language. It is an annual International Workshop recognized internationally in the formal syntax-semantics-pragmatics community. The 14th International Workshop on Juris-informatics (JURISIN 2020) details legal issues for the perspective of information science. This workshop covers a wide range of topics, including any theories and technologies which are not directly related with juris-informatics but have a potential to contribute to this domain.