One of the aims of science, perhaps its most fundamental aim, is knowledge of laws of nature. So if we want to know if the scientific enterprise can be rational, we need to see if there is some method by which one can attain knowledge of laws of nature.
All bodies fall with constant acceleration.
This contrasts with singular statements like 'this piece of copper expanded when heated' or 'that stone fell with constant acceleration'. BUT . . . . David Hume, an 18th century Scottish philosopher, argued famously that we can have no knowledge of general laws. We cannot have knowledge of general laws. Each of Hume's premises seems intuitively plausible. But the conclusion is one which most scientists and philosophers do not like.