The tale told in Sverre's saga is the official version. Historians have questioned the veracity of it, especially with regard to Sverre's alleged paternity. Some historians have considered his claim to be King Sigurd's son to be false, as did many of his contemporaries. Others have believed the paternal claim to be true, while most historians have found that the paternal question cannot be given a definite answer. Although the fact that kings fathered illegitimate sons was taken for granted, other facts indicate that Sverre was in his early thirties when he came to Norway, such as the age of his own sons and nephews. It has been cited against Sverre's claim that according to Canon law, one had to be at least 30 years old to be eligible for the priesthood. If Sverre was 30 years old when he became a priest, this would place his birth no later than 1145, making his paternal claim impossible, as Sigurd Munn was born in 1133. This particular objection has lost credence as it has become clear that this age limit was routinely ignored in Scandinavia at the time. However, other objections remain, such as the fact that Sverre consistently refused to undergo an ordeal by fire to prove his claims. At the time, such a trial was routine for new claimants to the throne, and belief in its efficacy seems to have been universal; yet Sverre refused to undergo it. If Sverre's claim was false, however, he would lack royal legitimacy, dooming his plans to failure. Regardless, his motivation is clear: to capture the throne of Norway, whether he could prove royal blood or not. After all, Norway had seen other claimants, since Harald Gille, whose paternity was equally questionable.