EMPIRICISM
What is empiricism?
Empiricism is an epistemology (theory of knowledge) based on the contention that knowing is an evidence-based activity, the evidence being that of the senses. Those convinced of the strong version of this epistemology claim to rely solely on the observations of experience and experiment for their knowledge of reality. Philosophers David Hume and John Locke were famous 16th century exponents of this claim, viewing it as a modern alternative to both mysticism (intuitively ineffable) and rationalism (synthetic a priori).
In other words, there is no knowledge intrinsic to the human mind, only what we learn from the environment. This view was developed to counteract claims to knowledge based on faith, divine revelation, or spiritual insight. Empiricists maintain that whatever faith, divine revelation, or spiritual insight might provide to the human mind, it was NOT true knowledge. The implication of their position is that the content of knowledge is the practical wherewithal for control. What their claim amounts to, is that the cognitive content that informs the exercise of control requires an exclusively factual basis. Initially this seemed a plausible claim, but as it turns out, even such practical aims as control in the "here and now" requires more than just the facts of the case -- additionally what is needed is some sense of the context AND an awareness of the purpose for which the control is being exercised.
How does empiricism work?
Initially modern empiricism was very liberating, summed up in that famous Americanism "I'm from Missouri, I've got to be showed". It is most effectively applied to the areas covered by the physical sciences, or to be more exact, material objects. But even forces (i.e., gravity, etc.) or processes (i.e., entropy, etc.) cannot be directly observed - only their consequences. We can see things fall so we hypothesize gravity, and we can measure the decline in free energy so we hypothesize entropy. Biological entities are still physical, but their complexity complicates the observational process to such an extent that hypothetical processes and functions are a necessary part of every description. Semiotic phenomena (involving symbols) add further layers to this complexity. Most human behaviours have hypothetical aspects as basic parts of their very existence and definition (i.e., money, marriage, meaning, etc.).
In every case, there are still facts, but although what we know is grounded in the facts, how the facts are gathered, processed, and interpreted is as important as the semantic content of those facts. So, in a comprehensive sense, what we know is partially empirical, but not entirely. Knowledge about the mass or density of a rock may be predominantly empirical, but knowledge about the size or density of a problem may be only marginally empirical.
References
RATIONALISM
What is rationalism?
Rationalism has been used in two ways: (1) in a formal sense, it refers to systematic thinking (abduction, induction, deduction); and (2) in an informal sense, it refers to the practice of developing, having, and using good reasons for actions. Each of these refers to the "rationality of means", but the Ancient Greeks also had the concept of the "rationality of ends", the idea that reason could guide the choice of goals as well as the choice of the wherewithal or instrumentality to achieve such goals. Both versions are epistemologies, theories of knowledge. Most modern notions of rationality tend to focus exclusively on the means, either ignoring ends altogether, or arguing that commitment to goals is not a "rational" decision but rather an "emotive" one. Toulmin and Searle argue otherwise.
How does rationalism work?
Formal rationalism does not deny the role of sense-data in informing knowledge, but insists that "knowing" itself is the product of thinking rather than perceiving. So, the distinction with empiricism is that empiricism refers back to the grounds for knowing (sense-data) whereas rationalism refers to the cognitive processes of knowing (thinking). Since both are essential for a complete view of knowledge, the historical dispute between empiricists and rationalists regarding which is pre-eminent, is just an example of philosophical chauvinism. The distinguishing feature of systematic thinking is that elaborate rules and an esoteric jargon are used, often over-used. Informal rationalism, reasonableness, involves having good reasons for both means and ends, thinking things through to the extent feasible, anticipating implications and consequences, and inferring an explanation or action to the best of one's ability - in other words, being mindful of one's circumstances, and seeking and applying life-lessons learned.
The older concept of "reason" covers both formal and informal versions. In ancient philosophy one used reason by drawing on whatever relevant knowledge was available to make decisions and choices. In the case of technical subjects, algorithms for processing variables were developed, and are the basis for theory today. In the case of ordinary experience, heuristics that serve as guidelines to clarification are often sufficient. Knowing what kind of a situation you are in, and when either formal or informal approaches are appropriate, is the goal that all practitioners strive for.
References
Stephen Toulmin
RETURN TO REASON
Harvard University Press, Cambridge, 2001
John Searle
RATIONALITY IN ACTION
MIT Press, Cambridge, 2003