How could you know? IMHO, our ability to intuitively correlate, often with very imperfect knowledge, is what makes us great guessers. I think most human correlations (where there is smoke, there is fire) are likely to be correct. However, we also need to be humble and we need to try to begin to understand our limitations and our tendencies toward hubris and self-deceit.
Highly simplified bayesian analysis. The universe of causal relationships is a subset of the universe of predictive relationships. The universe of predictive relationship (correlations) tends towards infinity. The universe of causal relationships is finite. Thus the likelihood that a predictive relationship is also a causal one is rather small and most correlations therefore are *probably* non-causal. Think of it as a Venn diagram where casual relationships are a tiny circle inside a much much larger circle of predictive relationships. Randomly throwing darts at the circle, you're much more likely to land outside the inner circle than inside it.