Matter refers to all living forms, plants and animals that respond to environmental stimuli: (sunflowers turn to the sun, amoebae move away from an acid solution). At this level, it does not necessarily involve sensation. 

Sensation  Most international law and welfare codes of practice equate sentience with the capacity to experience feelings when exposed to states such as pain, heat and cold, hunger and thirst. These feelings  may be aversive, attractive or unimportant. At this level of sentience, animals will be motivated to take action to adjust how they feel. By this definition, all vertebrates (mammals,; birds and fish) and an increasing number of invertebrates (cephalopods, some crustaceans ) are recognised as sentient, This number will increase as we lean more. 

Perception describes the ability to register, recognise and remember. It gives the ability to learn from experience. Pain (in humans) has been defined as ‘an unpleasant sensory and emotional experience associated with tissue damage’. All sentient animals feel pain. Animals with sentient minds can suffer not only the direct effects of pain but also chronic anxiety through awareness of its recurrence  from experience. Animals with the power of perception do not just live in the present. This increases their capacity to cope with the challenges of life but increases the potential for suffering if the stresses are too severe, complex or prolonged or if they are in an environment that restricts their ability to exhibit coping behaviour.

Mental formulation describes the ability to create mental pictures that enable animals to interpret and thereby get a fuller understanding of complex experiences, sensations and emotions. This not only enhances their ability to cope but also enriches their ability to pass on their skills to others, typically their offspring. 

Consciousness (as described by the Buddha) is restricted to the deepest circle of sentience and may be defined as ‘being aware that we are aware’. The extent to which non-human species may exhibit this degree of sentience is uncertain, but may be of minor importance in the context of their welfare. 

All sentient animal species experience stressful sensations such as pain, heat, hunger and thirst, as feelings  and this motivates them to action to relieve them. Species with the power of perception and mental formulation learn from experience how to cope with these and other stresses. This enables them to adapt to the challenges of their environment. If they discover that they are unable to cope, they will suffer. Species with the powers of perception and mental formulation (cognition) have sentient minds. Not only can they feel, they can think. Their actions in response to sensations both good and bad is modified by cognition.

Evidence is accumulating to show that animals with powers of perception, mental formulation and, in a few examples, self-awareness (consciousness), show behaviour consistent with higher emotions. These may include Comfort and Joy, Hope, Grief and Despair. Animals that have adapted to life in groups display complex patterns of social behaviour. They include education necessary to adapt to the fitness of  their society. Much of this behaviour is likely to be self-serving. However, some behaviour in some species may express empathy, concern, (including compassion) for others. If this is directed towards others with the same gene pool it cannot be said to be altruistic.

‘I would lay down my life for two of my children or eight of my second cousins’

J.B.S.Haldane

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