Because of the inherent structure of the SPT knowledge base, searches are best performed on its primary clusters of knowledge. An Overview of These are:
- Isomorphic Systems Processes
- Linkage Propositions
- Conventional Sciences
- Astronomy
- Cosmology
- Physics
- Chemistry
- Geology
- The Physical Sciences as a group
- Biology
- Molecular
- Genetic
- Cellular
- Organismic
- Ecological
- The Life Sciences as a group
- Mathematics
- Computer Science
- The Symbolic Sciences as a group
- Interdisciplinary Studies
- The Human Sciences as a group
- Information Categories