Historical particularism emerged in the early 20th century as a direct and critical response to the prevailing classical evolutionism of the 19th century, fundamentally reshaping anthropological thought and methodology. Classical evolutionists like E.B. Tylor and Lewis Henry Morgan proposed a unilineal model of cultural development, suggesting that all societies progress through a fixed sequence of stages (e.g., savagery, barbarism, civilization). They believed in psychic unity, implying that all humans possess the same mental capacities, leading to similar cultural developments independently. This approach was often ethnocentric, using Western European society as the pinnacle of civilization.

Franz Boas, the father of American anthropology, spearheaded historical particularism, rejecting the grand, universal schemes of classical evolutionism. His critique was multifaceted:

Firstly, Boas argued against the idea of unilineal evolution, asserting that each culture has its own unique history and trajectory, shaped by specific environmental, historical, and social factors. There is no single path of development that all societies must follow. This challenged the ethnocentric notion that non-Western societies were simply 'earlier' or 'less developed' versions of Western ones.

Secondly, historical particularism emphasized the importance of intensive, long-term fieldwork and the collection of detailed ethnographic data. Boas advocated for an inductive approach, where theories emerge from empirical observations rather than being imposed a priori. This contrasted sharply with the armchair anthropology of classical evolutionists who often relied on secondary accounts and speculative comparisons.

Thirdly, Boas introduced the concept of cultural relativism, arguing that a culture must be understood on its own terms, without imposing external standards or judgments. This was a direct counter to the ethnocentric biases of classical evolutionism, promoting an appreciation for the diversity and validity of different cultural practices.

Fourthly, Boas stressed the significance of diffusion—the spread of cultural traits from one society to another—as a major mechanism of cultural change, rather than solely relying on independent invention as posited by evolutionists. He also highlighted the role of historical contingency, where specific events and interactions shape cultural development.

In essence, historical particularism shifted anthropology from a speculative, comparative science seeking universal laws to an empirical, descriptive, and holistic discipline focused on understanding the unique historical and cultural context of each society. While later criticized for potentially overemphasizing uniqueness and making cross-cultural comparisons difficult, it was a pivotal development that laid the groundwork for modern anthropological fieldwork and the principle of cultural relativism, profoundly influencing subsequent theoretical schools.