How Many Human Senses are There?
There are between nine and twenty-one human senses, depending on who you ask, and how they define a sense. It is generally agreed that nine is the minimum. These are touch, taste, smell, sight, hearing, thermoception, nociception, equilibrioception, and proprioception. Hunger and thirst are also sometimes included. Generally, for something to qualify as a sense requires a free-standing sense organ associated with it. A sensory apparatus’ primary source of information should be force data originating from outside the brain. Thought or intuition is sometimes included as a sense, but this is incorrect. Human thoughts do not take data directly from reality, but rather from the confluence of sensory organs with which they are connected. Sometimes senses are perceived concurrently with each other, for example sounds that have colors associated with them. This phenomenon is called synesthesia, and is relatively rare, though often reported under the influence of hallucinogens or psychedelics.
• How in general should questions about the nature and number of animal or alien senses be answered? Answering these questions will in turn require a number of questions about the nature of experiences in different modalities to be addressed: • Are spatial properties represented differently in different modalities? • Must experiences in different modalities represent different objects and properties? • Do the proximal stimuli of the sense organs help to individuate the senses? For example, does visible light play an essential mediating role in vision such that creatures that utilise only ultra-violet or infra-red light lack visual experiences? • Are there a number of dimensions along which experiences in one modality can vary (e.g. pitch and loudness in auditory experience)? If so, what explains these dimensions and what is the relation between them and the mechanisms which realise the modality? Answers to these questions are of intrinsic interest, but they have a wider philosophical s
