1. An information processing device comprising: at least one processor configured to implement: an inference unit configured to obtain inference results by applying inference rules to context information; an inference result index value calculation unit configured to, by using information that shows a reading user who reads the inference results, acquire a knowledge level of the reading user corresponding to each of the inference rules that was applied until the inference results are obtained, and on the basis of each of the acquired knowledge levels calculate an index value that comprehensively shows depth of the knowledge of the reading user relating to the inference results; an inference result presentation unit configured to present the inference results on the basis of the index values calculated by the inference result index value calculation unit; and a knowledge level update unit configured to, for each inference rule that was applied until the inference results are obtained, update the knowledge level of the reading user about the inference rule concerned on the basis of evaluation information in which the degree of the knowledge that the reading user possesses is evaluated about the inference results presented by the inference result presentation unit, wherein the inference unit is further configured to make case information related to each inference rule that was applied until the inference results are obtained the inference results; and the inference result index value calculation unit is further configured to calculate the index values for each case information as the inference results.