This entry speaks to the nature of the individual element. Individualism says that the individual element is an independent entity that has self-contained properties, though, of course, it draws on resources around it. An example is the popular idea that the individual is responsible for his/her own fate. Your success and failure depend ultimately on how hard you work.
Holism says that the individual element is inextricably tied to other individuals. Individuals are interdependent, and they are internally related in the sense that each is imbued with, and constituted by, the qualities of others. An example is a child in a family. The child's psychology depends utterly on the way he/she is treated. Any intrinsic tendencies are modulated and mediated by experience. From this perspective, the child is not entirely responsible for his/her behavior.
Holism regards individuals or elements as reciprocally influencing each other. The child affects the family while being affected by it. This dialectical relation of individuals/elements comprises a system, or a whole. The whole is composed of individuals and affected by them. It is not independent of individuals. However, the whole is not simply a sum of independent individuals sequentially summed together, one after the other (see the entry on reductionism). The whole is more than the sum of the parts.
Solomon Asch explains the holistic nature of social interactions in the case of two boys carrying a log. The boys adjust their actions to each other and to the object. The two do not apply force separately. There is a unity of action that embraces the participants and the common object. This performance is a new product, unlike what each participant would do singly and also unlike the sum of their separate exertions. What each contributes is a function of his relation to the other, how the other acts. The other's actions lead to changes in the self's behavior. Self is permeated by other. Larger social units, such as teams and institutions, manifest other kinds of emergent properties.
Emergence is central to holism. It denotes the fact that the whole is different from the sum of the individual constituents. This whole then affects the qualities of the constituents. They are not self-sufficient, independent qualities.
These examples illustrate how the two approaches construe the nature, or existence, of the individual. These ontological perspectives of individualism and holism entail corresponding epistemologies, or ways of acquiring knowledge.
An ontology that construes individual elements as self-contained and self-determining, and as combining arithmetically to form groups, necessarily insists that knowledge of things consists of reducing complexity to simple, separate individual elements --e.g., a group is simply a collection of individuals co-existing. An ontology that construes elements as part of a system of relations that constitute them, insists that knowledge of things requires understanding elements as complex, multifaceted entities that are dialectically related to other things and embody their features.
Individualistic and holistic ontologies and epistemologies also entail distinctive methodologies.
Methodological Individualism
Positivism
Methodological individualism is the hallmark of positivism. Positivism construes phenomena as simple, homogeneous, separate, variables. A variable is defined as qualitatively invariant, and only quantitatively variable. The reason it is qualitatively invariant is because it is separate from other variables. This prevents others from imbuing it with their qualities, altering its quality, and complicating it. Intelligence, depression, aggression, and all other psychological phenomena are construed as separate variables with simple, fixed qualities.. Only their degree varies in different conditions. This ontology leads positivists to concentrate on measuring quantities of variables. They eschew investigating, or theorizing about, their qualities which are taken for granted as obvious, simple, and fixed.
Methodological individualism is also evident in positivistic instruments such as questionnaires. Each item on a questionnaire is a separate (discrete) element that supposedly taps a discrete psychological attribute. Items are randomly presented in order to prevent any association among them that would bias the subject away from responding to each one independently. In addition, each response is treated as a separate element that is accorded equal weight, and can be summed with the others. Sums are indifferent to the order of the elements. 5 + 3 + 1 is the same sum as 1 + 3 + 5. Sums presume that items are independent of each other, and that a 5 at the beginning is the same as a 5 at the end of a sequence. Of course, responses are statistically correlated together (e.g., in factor analysis). However, it is a correlation of separate, independent items.