In what sense is alchemy (in the way Newton understood it) not science?
It was a reasonable hypothesis at the time that you can make gold from other material. Indeed with particle accelerators you can do this [1, 2, 3]. Newton's methods were not powerful enough to achieve this, but this research hypothesis got refined, leading to chemistry as we know it today.
That's a fair question which is why I also included Newton's work on religion, which was apparently something of an obsession.
My answer is that humans--even really extraordinary ones like Isaac Newton--don't divide knowledge into scientific and non-scientific spheres.
Moreover, commonly used analytic tools like inductive reasoning that are helpful in science don't answer questions like what happens when we die in a very satisfactory way. Even in much more mundane questions humans tend to see patterns where they don't exist. [0] It's still an open question which types of problems are properly the domain of science.
My answer is that humans--even really extraordinary ones like Isaac Newton--don't divide knowledge into scientific and non-scientific spheres.
Moreover, commonly used analytic tools like inductive reasoning that are helpful in science don't answer questions like what happens when we die in a very satisfactory way. Even in much more mundane questions humans tend to see patterns where they don't exist. [0] It's still an open question which types of problems are properly the domain of science.
[0] https://en.wikipedia.org/wiki/Clustering_illusion