What does holism, as an ethnographic practice, permit the anthropologist to achieve; what are the weaknesses and strengths of such an approach?

Holism, first developed by Jan Christiaan Smuts (who was also the second Prime Minister of South Africa), is the idea that all systems should be viewed together rather than as separate parts. Just as physical systems are connected in the universe, so do human systems need to be examined together. 
As applied to anthropology or ethnography, holism means that cultures can best be understood by looking at the whole culture, not just its parts. Holism in anthropology usually involves taking a "four-field" approach that includes linguistics, physical anthropology, archeology, and cultural anthropology or social anthropology. All approaches should be used to understand a person or people.
The advantages of holism is that an anthropologist can get a broader view of a people or social structure in a more complex way that integrates different types of approaches. Cultures are complex, and this approach appreciates their complexity. The disadvantages are that such an approach may not be as rigorously scientific as other approaches because holism involves an element of subjectivity or judgment. In addition, holism results in observations that are at times uncertain and not conclusive, as holism produces theories.