The Quest for Sentience: from Crustaceans to Plants

Abstract Although the use of the term “sentience” in philosophy dates to the 17th century, its use expanded particularly in the second half of the 20th century, with the emergence of non-anthropocentric ethics. A search for sentience in the animal kingdom began, which required the identification of a set of evidential sources. The difficulty in establishing, beyond any reasonable doubt, the existence of sentience in animals more distantly related to humans, and the consequences that the matter has for the legislation on animal protection, led to the proposal to apply the precautionary principle in animal welfare policy. This principle establishes that the fulfilment of minimum criteria is enough for the existence of sentience to be admitted. This led to the attribution of sentience to invertebrates, namely molluscs, insects, and crustaceans. As a result, the possibility of including decapod crustaceans into animal legislation is currently discussed. In this article, we will perform the comparative exercise of applying a framework of minimum criteria of sentience, previously applied to crustaceans of the order Decapoda, to vascular plants. The framework is composed of eight independent criteria and the likelihood of plants meeting each of them will be assessed and discussed in the light of the existing empirical evidence.