Leonardo distinguishes between what an experiment actually shows and the conclusions people draw from it. Experience, in this sense, provides observations and results; error enters when a person expects an outcome that the evidence does not support or interprets the result according to a mistaken assumption.

The statement anticipates a central principle of scientific enquiry: conclusions should follow from observation rather than from expectation. Experiments can challenge an idea, but investigators must be prepared to revise their reasoning when the observed effects differ from what they predicted. The problem is therefore not necessarily with experience itself, but with the judgement imposed upon it.

The quote can be applied when assessing experiments, evidence or practical tests. It encourages separating observed results from prior beliefs and examining whether a claimed cause genuinely accounts for the effects that have been measured.