Cheat mode:
Choose the "Codes" selection at the "Options" menu. Then, enter one of the following codes to activate the corresponding cheat function.
God mode:
Enter Vitruvian Man as a code. Note: This must be used for both Robert and Sophie, as the game will end if either dies.

Double health:
Enter Sacred Feminine as a code.

One hit fist kill:
Enter Phillips Exeter as a code.

One hit weapon kill:
Enter Royal Holloway as a code.

Level select:
Enter Clos Luce 1519 as a code.

All Visual Database entries unlocked:
Enter Apocrypha as a code.

All bonuses unlocked:
Enter Et in Arcadia ego as a code. This will unlock all levels (including the M0X Louvre level and the M0X Rosslyn level), all Visual Database entries, the music Orrery, all concept art in Rosslyn, all Louvre paintings that are displayed in the substitution puzzles, and all anagram puzzles in Rosslyn.