Foundation of Problem Solving I have a feeling you're conflating trial and error with brute search. — TheMadFool
Maybe it worth to clarify a bit. In short no, there is a clear separation but it may be not too obvious at the beginning. I used a term "exhaustive search" for brute search and it isn't natural for people unlike trial and error.
When you are using trial and error method it may really looks like random attempts from the point of view of a solver, but it much more complex under the hood (I hope you took a look on articles that I mentioned previously). First of all, all our guesses aren't random, they are prioritized according our problem representation and prior knowledge. Secondly, every trial has two purpose: to guess a solution and to learn more about the system.
So fifteen puzzle is edge case of trial and error method. You are trying "random" moves and at some point the next move become obvious to you. Until the last row... that's where direct intervention into the solving process is required, but still, I know several people who was able to solve it without thinking about it deeply.
With several trials you can form an understanding of the system to estimate an appropriate guess for the next trial. In that sense trial and error method may look like a gradient descent method. You don't need to check each and every case, you just need to estimate the direction of the gradient. Most amazing part is that such an algorithm is wired into our brain so we don't even need to think about all this stuff, we are just trying to guess a solution...
It's almost impossible to solve the Rubik's cube that way. Trial and error method works amazingly well in case of smooth and continuous search space, but Rubik's cube is a discrete system and it's far from smooth. Fifteen puzzle is relatively simple to solvable only because of limited degrees of freedom that limits search space.
Exhaustive search is very painful for trial and error method too. Search process is optimized for speed. Every guess has a priority and we tend to completely ignore low priority guesses. There is well known phenomenon named a "blind spot", and for every professional it's a really hard work to eliminate all of them. So in case of chess you may completely ignore bishop for example, because you don't have a good prior knowledge of using it.