posteriori, justification is a phenomenon to which a great number of philosophical directions can be applied. After defining the issue of justification, foundationalism and phenomenalism will be expounded for their strengths and weaknesses in terms of a posteriori justification.
A Posteriori Justification
The phrase "a posteriori" refers to propositions that are knowable on the basis of experience. Experience is thus used to justify the knowledge of the proposition. Experience therefore forms the basis of knowledge, which makes this kind of justification empirical. The knowledge can be proven by the experiences beforehand. This past experience then forms the basis of a posteriori justification, and for thinking that propositions of this kind are true. Things that can be proven by the experiences of oneself can be classified as a posteriori. The research done by natural sciences for example are experiences upon which to base justification.
In terms of a posteriori justification, foundationalism probably makes most use of this paradigm in its theories. There are four different directions within this philosophy, each using empirical justification in its unique way. These include rationalism, Platonism, positivism and sciencism.
Rationalism is founded upon the theories of Descartes. Descartes uses his rational thought as empirical proof of his own existence, as well as that of the rest of the universe. The foundation upon which the theory of being in terms of rationalism is based, is the experience of thought within the mind, which leads to the sensory inputs relating to the world.
Platonism is based upon the belief that all persons are looking for something that is good, and that will last a lifetime. According to Plato, finding this would bring about happiness. It is presumed that Plato based this theory upon his own experience, and that thus those who subscribe to the theory also base it upon Plato's presumed experience. This belief is then also based on a posteriori evidence.
Positivism is perhaps the most a posteriori based theory among the foundationalist directions. All theories relating to theology, metaphysics, or other non-physical directions are rejected on the basis that they cannot be scientifically proven. Based on experiences that can be perceived by the senses, positivist theories revolve around knowledge and science. In addition to theories about knowledge, other a posteriori justifications in terms of positivism can be applied to theories of society, morality, language and mind. These theories are all based upon evidence gained from rational, scientific inquiry.
The theory of society for example examines the static and dynamic laws governing society. This theory is based upon an experience of society that is denoted into the two categories of static and dynamic. Statics govern the laws of action and reaction in the social system, while dynamics relate to social succession. Furthermore, sociology is seen as the "true final science," as it is observable in human society, and can be studied scientifically and experientially. The positivist theories of language and the mind are similarly based upon what can be observed; language is seen in correspondence with facts, while the mind is seen as biological instead of psychological.
Sciencism, the final leg of foundationalism, sees science as the basis of all knowledge. This can also be seen in terms of a posteriori justification, in that it is a collection of observable, experiential facts.
Foundationalism holds three positions in terms of justification for basic beliefs. The first of these is moderate foundationalism, according to which basic beliefs are in themselves sufficient to justify the condition for knowledge. Thus, no further justification is required. In a greater degree, the same is true for strong foundationalism. According to this paradigm, logical infallibility is applied to basic beliefs. The justification then relies upon the assumption of logical infallibility. The third position is weak foundationalism. There is a very low degree of empirical justification for these beliefs, and these beliefs are therefore not adequate to justify further beliefs based upon the original belief. All of these beliefs are based upon experience, and thus can be seen as justifiable in an empirical sense.
In terms of empirical justification then, foundationalism offers a variety of viewpoints. This perhaps makes it a stronger application for the use of empirical justification, as it appears more flexible than is originally the assumption. Empirical justification thus relies on the fact that the basic belief is assumed to be adequate. Such basic belief is then used as a foundation for further beliefs. It is however also interesting to note that once the basic belief, which is based upon experience, is not questioned once it has been formed. No further experiences by further persons alter the original belief. This is especially seen in Platonism and rationalism. It is also interesting to note that weaker foundationalism can be strengthened in terms of empirical justification in conjunction with other theories, such as coherentism.
In terms of foundationalism, coherentism is often used to supplement the inadequacies of weak foundationalism. Indeed, coherence is relied upon where empirical justification fails in terms of weak foundationalism. The claim here is that increased coherence would make for an increased likelihood of empirical justification, despite the fact that weak fundamentalism in itself is not adequate to do so.
In general then, the three directions that can be taken by fundamentalism make a strong case for empirical justification, as a number of elements are involved. In the case of weak justification, coherentism serves as a strengthening factor for justification.
In itself, it appears that coherentism is inadequate as an empirically justifying factor. It has to be used in conjunction with other theories in order to achieve empirical justification, and yet justification can also not truly exist without coherence. This is the system by which empirical justification can be certified as reliable. For coherentism, the very property of coherence itself serves as the justifying factor for beliefs or knowledge. This is only reliable in cases where the original system, such as foundationalism, is involved. Coherentism in itself is not adequate to truly provide an empirical justification for beliefs.
Phenomenalism is close to Descartes' theory of rationalism, as all physical objects and events are seen as reduced to being perceived by the mind. All that is physical therefore, is mental, as the mind is used to observe all physical phenomena. This theory is then also based upon the human experience, and thus is empirically justifiable. Physical objects are then seen as bundles of data arriving in the brain through the senses.
It is thus believed in phenomenalism that there exists no external world apart from the one observed and experienced by the mind. This is reminiscent of both Descartes and skepticism. According to Descartes, the external world exists because the mind observes and experiences it. According to skepticism, no empirical proof can be offered for the external experience of the world, simply because it is all observed by the mind. Human experience is thus highly subjective and possibly deceptive; thus a posteriori justification becomes unreliable and void. Skepticism opposes all empirical knowledge as defeated by the possibility of being deceived by one's own perceptions or indeed outside forces. The main argument is that an empirical proposition such as the fact that there are trees, cannot be empirically justified, because the human mind might in fact be deceived by elements such as being only an hallucinating brain.
According to skepticism then, justification cannot be a necessary condition for knowledge, because of the variety of ways in which a human mind is able to be deceived. Other possible deceptions include outside sources such as demons, or sources from within such as illness.
Phenomenalism is thus very close to both Descartes and skepticism -- being that all observable phenomena are in the mind, it is logical to assume that it is likely that nothing outside of the observing mind exists. This is part of the proof offered by the phenomenalist experience. Thus, if a posteriori justification is sought for the position of the phenomenalist, only the experience of the observing mind can be accepted as proof for the non-existence of the outside world.
On the other hand, phenomenalism also denotes a reality that is entirely independent of a conceiving mind. This reality then is also impossible to justify empirically, as it is exterior and perceived as impossible to exist. Objective reality as experienced by all human beings is empirically justifiable by the harmony of perceived mathematical laws. This justification is also fairly strong, as there appears to be something that can be justified in an objective manner. Yet the argument is not as strong as that of phenomenalism, as there appears to be a hidden "true" reality that cannot be empirically justified, because it cannot be perceived as possible.
It is clear that the question of a posteriori justification can easily lead to the assumption that nothing outside of the mind exists. In this, certain areas of foundationalism and phenomenalism agree in terms of justifiability. The better position for empirical justification can be seen to be foundationalism, as experience appears…