Defining Category Membership

In trying to understand scientific and everyday concepts and categories several approaches  have been taken.

Traditionally logical positivism has attempted to identify concepts and categories by breaking them down to their elements (like Locke's elements of the mind). Here the assumption is that if we know the set of distinctive features we will know the class or category.

Defining features approach states that a set of features (characteristics) are present in every member that define each category. See figure 8.4

However it can be concluded that 'natural kinds' or categories often have members with some but not all of the defining features of the class or category, rather that there are fuzzy boundaries around class membership.

Ludwig Wittgenstein, alternatively has suggested that concepts and category members share family resemblance.

Family Resemblance refers to the property of category members to vary from each other, but still share a subset of the total set of features in of the 'family' of members that make up the category.

E.g. figure 2.