Thinking in English words makes &quot;clean&quot; and &quot;dirty&quot; sound like single-dimensional vectors that directly oppose each other. But that&#x27;s not true. What is actually true is an n-dimensional vector, with an enormous variety of &quot;cleans&quot; and &quot;dirties&quot;, and even more complicated when you start combining the vectors. Plus you don&#x27;t get to custom-design them; you have to take what exists in the world. So when you &quot;clean&quot; yourself with a certain soap of the &quot;dirtiness&quot; you currently have, you don&#x27;t get to custom design a cleaning agent that precisely knocks out only the portions of the &quot;dirty&quot; vector you have, you can only use things that exist, with all their side effects.<p>A lot of things in the real world work like that, but the medical world, since it involves biological bodies, the most complicated things in the known universe, seem particularly prone to this problem. Similarly, if you have a genetic disease where X is overexpressed, but its action is opposed by Y, it isn&#x27;t necessarily a solution to just increase the expression of Y, because where English makes &quot;oppose&quot; sound nice and clean, in reality that&#x27;s a summation of two complicated vectors. For all you know, X and Y also have a way in which they work in the same way, and having a system that overexpresses both will suddenly expose a pathology where the combination of both becomes fatal even so. Biology&#x27;s a nasty place. The engineering is profoundly non-human.