If by “method” all one means is a short or best way of discovering truth, and this truth rest primarily on vision and not on any ability to generate some product (like radar or an atomic explosion), then there are many good proposals for metaphysical method. Deciding between them is simply a matter of reading the arguments and thinking real hard.
But what gives scientific method such a forceful and unignorable claim to truth is its ability to inform modes of engineering (not just of mechanical engines but also biotech and information systems). The muscle of scientific method is its ability to engineer things, not just obvious consumables but, more essentially, the experiments that we can point to as real instances of the physical models we have conceived of and engineered. Metaphysics does not have an ability to inform a practical science corresponding to its object. To someone who sees the muscle of a method is its power to engineer, metaphysics will seem weak, ineffectual, and hopelessly lost in a diversity of unresolvable opinions.
But just as a complete engineering would be able to reproduce all possible physical systems, “metaphysical engineering” approach a state of being able to reproduce existence simply. It would model not just interactive systems governed by physical laws but all realized or even realizable modes of existence and action. Here’s the problem: some modes of existence are simply non-reproducible, e.g. anything unique considered in its uniqueness. This includes not just anything that had an identity of what it was and its singular existence but anything that must be related to personally – things that must be a “you”.
To have a metaphysical engineering would require a mind that, in bringing something forth, could bring forth something essentially unique, that is, a mind that could bring forth what was truly unrepeatable. The generation of the trinitarian persons would be the (logically) highest such instance of this, but any generation of an individual in its individuality – what is usually just called a thing that actually exists – would require a degraded form of this same generation.
But then if all knowledge is complete only when there is some supposed engineering behind it, and generation is always essentially of the unique, then complete knowledge of generation, if possible, requires a mind that can conceptualize the unrepeatable. Such a knowledge is divided irreducibly from the experimental, which demands repeatability; and it would not fall under a law, which is defined by its being repeated.