 At play in these various forms of skepticism are several underlying assumptions. Among other disagreements, researchers disagree about what life is, whether it is a natural kind with an essence or a human construct; they disagree as to the purpose of defining life, especially if it will not change scientific practice; and they disagree as to the features of life that are relevant and the ones that are mere consequences. When researchers hold unstated assumptions such as these, they are liable to mistake the source of their disagreement.