Scientific understanding is ultimately derived from a combination of ceteris paribus (all other things being equal) statements. Causal necessity can be established, even when it appears that the examined phenomena do not display one ceteris paribus statement or the other.
If employment increases after a raising of the minimum wage, it could never be assumed that the increased minimum wage caused the rise in employment, because (artificially) higher wage costs mean decreased supply of jobs and lower demand ceteris paribus.
There must be other factors involved to explain the rise in employment, such as the discovery of new natural resources or the popularization of an avenue for jobs (e.g. the internet), the increase in jobs of which it must be assumed have offset the loss of jobs that have become obsolete from it. These additional factors themselves are also essentially ceteris paribus supply/demand/price relations.
To assume that it is the minimum wage itself that increases employment is to defy causation itself. Whatever peculiar instances are involved in one situation provide the explanations, which themselves require causal necessity.