The time of electromagnetic decay of the Sun's general magnetic field is shown to be 10 10 years, suggesting that the field may be a relic from a different primeval state. An alternative hypothesis, ascribing the field to thermal effects due to convection in the rotating Sun, is shown to give a field of the correct sign, but less than 10 −7 times the observed field; and a modification of the hypothesis, supposing that the field due to thermal currents is magnified by dynamo action, is shown to demand over 10 18 years for the field to grow to its present size. Other possible explanations of the Sun's field are suggested. In an Appendix, the effect of the Sun's rotation on turbulence in its interior is briefly considered.