Within the debates reviewed in this paper three separate but related questions can be identified:
1)Are cells independent entities, both morphologically and physiologically speaking? Closely related to this question are those regarding whether higher plants and animals are compound arrangements of distinct cell units or some other arrangement in which the cellular structure plays only a secondary role; have the Metaphyta and Metazoa evolved from colonies of social protists or by the internal formation of cell membranes within an originally multinucleated ciliate?
2)Do the causes of the embryological development of specialized tissues and organs lie in the individual cells or are cells themselves the effect of a more fundamental organization which is dispersed throughout an original protoplasmic mass, (the ovum), whichis inherited from parent organisms? In other words, do the cells build the organismor does an organism build the cells?
3)Are cells themselves elementary or composite ? Are they the fundamental and primary units of life or might they perhaps be colonies of even more elementary vital units?
At the heart of the cell state theory is the age-old philosophical question concerning the relationship between part and whole, the One and the Many.
Indeed, as Georges Canguilhem (1969, 62) has written: The history of the concept of the cell is inseparable from the history of the concept of the individual.3 The cell theory, and the metaphor of the cell state in particular, forced biologists to consider the essentially philosophical question, Am I a One or a Many? Virchows response was that the philosophers I is the result of the biologists We (Virchow [1859] 1958, 139). But the debate that ensued regarding whether humans and other animals are to be construed as single organisms or colonies of cells required biologists to tackle other fundamental and essentially philosophical questions regarding the definitions of a colony and individual. Arriving at the correct conception of the organic individual has proven to be a perplexing task. Is it the cell? Is it a multicellular organism in which the cells are obligately interdependent upon one another? Can a community of organisms a super-organism count as an individual? Can a species? Can they all count as different levels of individual? These are questions which continue to attract the attention of philosophers and biologists, especially those concerned with the units of selection problem.
Answering these questions involves grappling with the question of the degree of autonomy each level or unit might be said to possess. Ultimately, beginning in the first decades of the twentieth century, the metaphor of the cell as an autonomous citizen within a larger social body lost its allure. At this time biochemical and physiological investigations began to replace morphological and evolutionary considerations of organisms and cells. As biochemistry matured as a professional discipline, another metaphor came to dominate, one more suited for the particular types of questions being pursued by the new breed of investigators, so that today one more commonly hears the cell described as a chemical factory.
