 The hypothesis that the word "horse" refers to all "animals of this species" is most likely of the three possible definitions, as it has both a reasonable prior probability and likelihood given examples.Bayes' theorem is important because it provides a powerful tool for understanding, manipulating and controlling data5 that takes a larger view that is not limited to data analysis alone6.The approach is subjective, and this requires the assessment of prior probabilities6, making it also very complex.