What is absolutely fundamental and non-reducible -- the fewest number of categories within which everything can be classified.
| Name | Type | Role | |
|---|---|---|---|
| Luke Barnes | Guest Star | ||
| Raymond Tallis | Guest Star | ||
| Robert Lawrence Kuhn | Guest Star | ||
| George F. R. Ellis | Guest Star | ||
| Barry Loewer | Guest Star | ||
| David Albert | Guest Star |