# Theory

How IIT's quantities map onto PyPhi's types and functions, grounded in a
single worked example. For a broad orientation to the theory itself, see also
the [IIT wiki](https://www.iit.wiki); the authoritative sources are
[Albantakis et al. (2023)](https://doi.org/10.1371/journal.pcbi.1011465) and
[Mayner, Marshall & Tononi (2026)](https://doi.org/10.3390/e28040410).

```{toctree}
:maxdepth: 1

overview
substrate-and-system
conditional-independence
system-integration
intrinsic-information
distinctions-and-relations
phi-structure
macro-units
computational-complexity
```