Sometimes success is carried by knowing when you are wrong, and making it right. Even very knowledgeable people have bad ideas. A rule going into the skill system for Lovecraft RPG is the notion of Expertise. If you have a skill, you have it. If you don’t have a skill, you can try to solve a problem using related knowledge. But it takes real skill and practice at anything to know what the bad practices are.How Expertise works is simple. If you have 1D in a Skill, you automatically have some. Having Expertise lets you increment your highest number Fail on a D6 roll (1-3 being a Fail, 4-6 being a Success). The highest number Fail is a 3, so if you roll a 3 (and only one), then you can increment it to a 4. That is turning around one process or idea that wasn’t so good, polishing and improving it to make it work.
But you only get one increment with Expertise, is that it? No. For each D of skill in the roll, you can decrement your lowest D by 1. If you have and use a skill rated at 1 D, and you roll a 1, you can decrement that to a 0. That Fail then is removed from your balance of Fails and Successes.