Descartes first invokes the errors of the senses in the Meditations to generate doubt; he suggests that because the senses sometimes deceive, we have reason not to trust them. This use of sensory error to fuel a sceptical argument fits a traditional interpretation of the Meditations as a work concerned with finding a form of certainty that is proof against any sceptical doubt. If we focus instead on Descartes's aim of using the Meditations to lay foundations for his new science, (...) his appeals to sensory error take on a different aspect. Descartes's new science is based on ideas innate in the intellect, ideas that are validated by the benevolence of our creator. Appeals to sensory error are useful to him in undermining our naïve faith in the senses and guiding us to an appreciation of innate ideas. However, the errors of the senses pose problems in the context of Descartes's appeals to God's goodness to validate innate ideas and natural propensities to belief. A natural tendency to sensory error is hard to reconcile with the benevolence of our creator. This paper explores Descartes's responses to the problems of theodicy posed by various forms of sensory error. It argues that natural judgements involved in our visual perception of distance, size and shape pose a problem of error that resists his usual solutions. (shrink)