Level select
Enter "Clos Luce 1519" as a code at the "Codes" screen under the options menu to unlock all levels.

Invincibility
Enter "Vitruvian Man" as a code at the "Codes" screen under the options menu. 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 at the "Codes" screen under the options menu.

One-hit fist kill
Enter "Phillips Exeter" as a code at the "Codes" screen under the options menu.

One-hit weapon kill
Enter "Royal Holloway" as a code at the "Codes" screen under the options menu.

All Visual Database entries
Enter "Apocrypha" as a code at the "Codes" screen under the options menu to unlock all Visual Database entries.

All bonuses
Enter "Et in Arcadia ego" as a code at the "Codes" screen under the options menu. 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.