Image: UbisoftOfficial screenshot from Ubisoft.
This Joseph: Collapse trophy asks you to collect all of Joseph's Diary Pages in Joseph's mind. It is a pure collectible hunt spread over the whole map.
Search every area of Joseph's mind and pick up each one as you find it. A collectibles guide or map helps a lot, since some are tucked away.
Upgrade your health and movement Traits first so you can explore without dying. Unlock all three Safe Houses to cut down on walking.