The secrets revealed.
Every trophy in The Witness, other than the Platinum, is hidden. The list is quite short at only 14 trophies, but it is made up of eleven golds, two silvers and the one aforementioned platinum. The list is also quite easy with 11 of the trophies being awarded for activating one of the game’s lasers. Below outlines what exactly is required to unlock each of The Witness’ hidden trophies.
Shady Trees (Gold)
Activate the Shady Trees Laser (Walkthrough)
Activate the Symmetry Laser (Walkthrough)
Desert Ruin (Gold)
Activate the Desert Ruin Laser (Walkthrough)
Activate the Treehouse Laser
Activate the Keep Laser
Activate the Quarry Laser (Walkthrough)
Activate the Marsh Laser (Walkthrough)
Activate the Jungle Laser
Activate the Monastery Laser (Walkthrough)
Activate the Bunker Laser
Activate the Town Laser
Reach the End
Complete a certain challenge
As this above list makes clear, the trophy list for The Witness is not particularly difficult but could be quite time consuming. For the constantly updating The Witness wiki, including solutions for puzzles that do not activate lasers, see here.