Last Piece Fallacy
I've been very into self-compassion lately, because it feels like the thing I didn't know I was looking for all of my life. It's a balm that made it possible for me to relax in my skin again. But when I evangelized the panacea of self-compassion, my friends' efforts made me realize that it does not work in a vacuum. I was only able to have such rapid success with self-compassion because I had a lot of practice with its pre-requisites. In fact, self-compassion wasn't the single cause of my enhanced wellbeing.
I want to propose something called the "Last Piece Fallacy,1" which is when you attribute an effect entirely to the addition of the last ingredient that was added. (If this is already a named fallacy, please point it out, because I couldn't find it.) It's a special case of the "Single Cause Fallacy" because all the ingredients are necessary, work together to create the effect, and it's the addition of the last cause that creates the full effect, so it is fallaciously considered the only cause as opposed to one of several not necessarily interdependent causes being implicated as the one true cause. I've seen it in many places, but it looms particularly large in matters of the mind.
For instance, I think this is why mindfulness meditation is such a revelation to some people and not to others. For some people, noticing your thoughts and getting distance from them is the last piece. The implications of mindfulness are obvious to them as soon as they experience it. I have put a lot of time into developing mindfulness skills and challenging myself with meditation, but at no time did the practice feel like a revelation. However, the skill massively contributes to my ability to recognize my thoughts and feelings somewhat objectively, which is is so important to the practice of self-compassion that it's the first of the three elements of self-compassion. The other two elements, self-kindness and common humanity, were new to me. When they clicked into place, the way was paved and self-compassion felt like the final piece in discovering a new way to relate to myself and my experience.
But it could easily have happened the other way. In fact, I would probably have picked up mindfulness faster if I had really understood or believed in self-compassion first. My reaction to catching myself distracted was always harsh for about the first two years I did serious meditation. I knew I wasn't "supposed" to react like that, but, sadly, I didn't know any other way. In parallel to strengthening mindfulness, I was developing moral and philosophical beliefs that allowed me to appreciate the moral importance of all conscious beings without exception. That belief never gave me psychological comfort because it just feels like a fact. (Usually thinking about it more deeply would just lead me to feel an outpouring of grief for all the suffering in the world.) But it laid the groundwork for me to grok the common humanity part of self-compassion, which is a source of spiritually meaningful connection. Finally, I went through some very hard things in the last two years that finally convinced me that I was trying the best I could and I was allowed to stop whipping myself. And then I was ready for self-compassion, and it felt like it changed everything.
I think a lot of mental health interventions are thwarted by Last Piece Fallacy. Either because it makes scientific study results inconclusive or because it makes your own personal experimentation more difficult. If something doesn't work for you, that might not always be the case with more learning and practice. Conversely, if in the realm of mental health something does work for you, it's probably not sufficient on its own to give you your result.
I've framed this in terms of mental and emotional health, because that's where the cost of this fallacy has been most obvious to me. But Last Piece Fallacy could be about anything in this world of so few necessary and sufficient single causes. Respecting the complexity and interconnectedness of all things might even be good for your mental health.
I think the "Catalyst Fallacy" would be snappier, but since the catalyst is not part of the final product, it doesn't technically apply to all the situations I have in mind. Another candidate I came up with, the "Trigger Fallacy" implies the result is an event, and I have more in mind a product.