 Fine tuning arguments contend that life would not exist were it not for the fact that multiple physical parameters (e.g., the cosmological constant and the ratio of the mass of the neutron to the mass of the proton) have numerical values that fall within a range of values known to be life-permitting that is very narrow compared to the range of values that are compatible with current physical theory and are known to be life-prohibiting. For example, even minor changes to the nuclear weak force would not have allowed for stars, nor would stars have endured if the ratio of electromagnetism to gravity had been much different. John Leslie observes: 