Constructivism is not a unitary theoretical position; rather, it is a continuum. The assumptions that underlie this continuum vary along several dimensions and have resulted in the definition and support for multiple types of constructivism. Typically, this continuum is divided into three broad categories: Cognitive Constructivism, Social Constructivism, and Radical Constructivism.

Knowledge is the result of the accurate internalization and (re)construction of external reality by an individual.

Knowledge is the result of social interaction and language usage, and thus is a shared, rather than an individual, experience.

Knowledge is constructed from individual experience, but is not, in any discernible way, an accurate representation of external reality.

Cognitive constructivism represents one end, or extreme, of the constructivist continuum and is typically associated with information processing and its reliance on the component processes of cognition. While emerging from the four, previously mentioned, epistemological tenets, cognitive constructivism only emphasizes the first two tenets, that is, that knowledge acquisition is an adaptive process and results from active cognizing by the individual learner. These particular epistemological emphases lead to defining principles that maintain the external nature of knowledge and the belief that an independent reality exists and is knowable to the individual. Knowledge then, from the cognitive constructivist position, is the result of the accurate internalization and (re)construction of external reality. The results of this internalization process are cognitive processes and structures that accurately correspond to processes and structures that exist in the real world. This claim, that reality is knowable to the individual, differentiates cognitive constructivism from both social and radical constructivism.

This process of internalization and (re)construction of external reality is learning. That is, learning is the process of building accurate internal models or representations that mirror or reflect external structures that exist in the "real" world. This perspective on learning focuses on (a) the procedures or processes of learning, (b) how what is learned is represented or symbolized in the mind, and (c) how these representations are organized within the mind.

Cognitive constructivism, as a learning theory, is often considered a "weak" form of constructivism, within the constructivist community, since it only embraces two of the four epistemological tenets. "Weak" in this case is not a value judgement, such as better or worse, but rather merely an indication of adherence to foundational assumptions. Thus , knowledge construction is considered primarily a technical process of creating mental structures, but has little bearing on the nature of the subjective knowledge within the mind.

Social constructivism lies somewhere between the transmission of knowable reality of the cognitive constructivists, and the construction of a personal and coherent reality of the radical constructivists. Social constructivism, unlike cognitive and radical constructivism, emphasizes all four of the previously mentioned epistemological tenets. These particular epistemological emphases lead to defining principles that maintain the social nature of knowledge, and the belief that knowledge is the result of social interaction and language usage, and thus is a shared, rather than an individual, experience. In addition, this social interaction always occurs within a socio-cultural context, resulting in knowledge that is bound to a specific time and place. This position is exemplified by Bakhtin (1984), "truth is not to be found inside the head of an individual person, it is born between people collectively searching for truth, in the process of their dialogic interaction" (p. 110). Truth, in this case, is neither the objective reality of the cognitive constructivists nor the experiential reality of the radical constructivist, but rather is a socially constructed and agreed upon truth resulting from "co-participation in cultural practices."

Like radical constructivism, social constructivism would be considered a "strong" form of constructivism, emphasizing all four of the epistemological tenets. However, social constructivists generally downplay the mental construction of knowledge (not because social constructivists do not believe in mental construction but because it is seen as relatively trivial) and emphasize the co-construction of meaning within a social activity. In this sense, social constructivism is more concerned with meaning than structure.

Radical constructivism represents the opposite end of the constructivist continuum from cognitive constructivism. Radical constructivism fully embraces the first three epistemological tenets, that is, that knowledge acquisition is an adaptive process that results from active cognizing by the individual learner, rendering an experientially based mind, not a mind that reflects some external reality. In addition, there is a current movement within radical constructivism to more fully accept the fourth epistemological tenet, thus recognizing social interactions as a source of knowledge. These particular epistemological emphases leads to defining principles that maintain the internal nature of knowledge and the idea that while an external reality may exist, it is unknowable to the individual. Reality is unknowable since our experience with external forms is mediated by our senses, and our senses are not adept at rendering an accurate representation of these external forms (e.g., objects, social interactions). Therefore, while knowledge is constructed from experience, that which is constructed is not, in any discernible way, an accurate representation of the external world or reality.

The adaptive nature of knowledge underscores that knowledge is not objective "truth," that is, internal knowledge does not match external reality, but rather is a viable model of experience. These viable models are created within an individual, influenced by the context within which an activity was experienced, and relative to the accomplishment of a particular goal. Thus, according to Staver (1995), "knowledge is knowledge of the knower, not knowledge of the external world; improving knowledge means improving its viability or fit in, but not match with, an external world" (p. 1126).

An evaluation of radical constructivism results in radical constructivism being considered a "strong" form of constructivism, as it fully embraces three of the constructivist epistemological tenets and at least partially embraces the fourth. That is, radical constructivism is concerned with both the construction of mental structures, the position of cognitive constructivists, and the construction of personal meaning. In this sense, radical constructivism involves a greater degree of construction than does cognitive constructivism, involving two planes of construction, structure and meaning, rather than only one, structure.