Presented in this document are essays related to a research project focusing on conceptual obstacles which confine and inhibit scientific understanding (conceptual barriers). These include a short summary of research activities; research methodology; outline of a theory and summary of supporting evidence related to conceptual barriers encountered in teaching science to adults; students' views on critical barriers; a taxonomy of critical barriers (focusing on pervasive barriers, barriers recognized in narrower contexts, and barriers related to mathematics); problems with mathematics; ecological contexts of critical barriers (psychological sources of learning problems, differences in personal learning styles, and problems with pedagogenic causes); clues from science history (biographical/historical sources of critical barriers); description of a college level "Man and Nature-Energy" course, including list of difficulties students encountered; and notes and reflections on the course by a participant/observer. A list of references, annotated list of relevant psychological literature, and the proposal submitted to the National Science Foundation (NSF) are included. The NSF proposal provides the rationale/background for and significance of the research. The document is associated with five additional volumes of detailed records. Contents of these volumes are included at the beginning of this document. (Author/JN)