The term "H. Stephen Chase" does not appear to be a widely recognized established concept or a prominent figure with extensive encyclopedic coverage under this exact spelling.
It is highly probable that the intended term was "H. Steven Chase." H. Steven Chase is a notable American psychologist known for his contributions to Relational Frame Theory (RFT), a psychological theory of human language and cognition, and its application within Contextual Behavioral Science (CBS). He is frequently cited alongside Steven C. Hayes and Kirk Strosahl as a key developer of RFT, which underpins Acceptance and Commitment Therapy (ACT). However, specific encyclopedic information directly pertaining to an individual named "H. Stephen Chase" (with "Stephen" as opposed to "Steven") is not readily available in widely recognized academic or public encyclopedic sources.