If pleasure is more open than pain to a double definition, first as a real sensation, second as a more indirect impression, it is clear that the calculus – the advantages of which Bentham praised so fulsomely − cannot be identical for pleasure and pain alike. Sensations may be combined in the infinitesimal calculus in a substantive way, but this is impossible for the more indirect reflective impressions, which require other sorts of mathematics. For Bentham, it is not a question of eschewing calculation, but of facilitating it, perhaps through a probability calculus in a Bayesian or subjective style. The theory of fictions permits the combination or substitution of the two aspects of pleasure, so that what seems to be an ambiguity in Bentham's approach to pleasure is really an attempt to render the concept useful, that is, capable of utilization in calculations bearing on important areas of practical policy.