Eclecticism

The grand foyer of the Palais Garnier, by Charles Garnier, 1860–1875. Stylistically, it aimed for a Baroque opulence through lavishly decorated monumental structures that evoked Louis XIV's Versailles. However, it was not just a revival of the Baroque, being more of a synthesis of Classicist styles, like Renaissance, Baroque, Rococo, Neoclassicism etc. Thus, it is an example of eclecticism in architecture.
Early Romanian Revival house on Strada Grigore Alexandrescu in Bucharest, Romania, unknown architect, c. 1900, that mixes Beaux-Arts and Romanian Revival elements and proportions

Eclecticism is a conceptual approach that does not hold rigidly to a single paradigm or set of assumptions, but instead draws upon multiple theories, styles, or ideas to gain complementary insights into a subject, or applies different theories in particular cases. However, this is often without conventions or rules dictating how or which theories were combined.

It can sometimes seem inelegant or lacking in simplicity, and eclectics are sometimes criticized for lack of consistency in their thinking. It is, however, common in many fields of study. For example, most psychologists accept certain aspects of behaviorism, but do not attempt to use the theory to explain all aspects of human behavior.

Eclecticism in ethics, philosophy, politics, and religion is often compared to syncretism, but the two concepts differ in their approach to combining elements from different traditions. While syncretism in religion involves the merging or assimilation of several distinct traditions into a new, unified system, eclecticism adopts elements from various systems without necessarily integrating them into a single cohesive framework. This distinction allows for a broader, more inclusive approach in eclecticism, where the selection is based on individual merit or preference rather than an attempt to create a new unified tradition.