Funny you'd say that, because that's precisely what Economists do... when you cannot determine preferences to predict economic behaviour, use economic behaviour to infer preferences. But then you can no longer predict economic behaviour, although you can pretend that you can...

Revealed preference theory came about because the theories of consumer demand were based on a diminishing marginal rate of substitution. This diminishing MRS is based on the assumption that consumers make consumption decisions based on their intent to maximize their utility. While utility maximization was not a controversial assumption, the underlying utility functions could not be measured with great certainty. Revealed preference theory was a means to reconcile demand theory by creating a means to define utility functions by observing behavior.