Suppose that you make a simple statement like "ice is cold." If someone asks you "How do you know that ice is cold?", one appropriate answer is to cite some "way of knowing." Some common "ways of knowing" are:

Thus, when asked how you know that ice is cold, you could answer "Common sense - my experience with ice - tells me that it is cold." The problem with this answer is that different people can have very different experiences. A native Antarctican, for example, might respond "You’re wrong. Ice isn’t cold. It’s wet and solid." You can also answer "Tradition - it is a common premise of my culture", or you could answer "Authority - pointing to the definition of ice in a scientific dictionary or high-school textbook". You could say "Religion - this is a pillar of my religion!". Yet, you could also say "Induction - i made observations as to the relative warms of different objects". Using "Science, you the following hypothesis "all objects which are frozen are cold". While each way of knowing has its strengths and weaknesses and all contribute to some forms of knowledge only some of them are used in the scientific process.

Although it is a false dichotomy in some respects - and an oversimplification in many respects - it is sometimes useful to think of empiricism and rationalism as opposing philosophical schools.

The inspiration of rationalism has always been mathematics, and rationalists have stressed the superiority of the deductive over all other methods in point of certainty. According to the extreme rationalist doctrine, all the truths of physical science and even history could in principle be discovered by pure thinking and set forth as the consequences of self-evident premises. This view is opposed to the various systems which regard the mind as a tabula rasa (blank tablet) in which the outside world, as it were, imprints itself through the senses.

The opposition between rationalism and empiricism is, however, rarely so simple and direct, inasmuch as many thinkers have admitted both sensation and reflection. Locke, for example, is a rationalist in the weakest sense, holding that the materials of human knowledge (ideas) are supplied by sense experience or introspection, but that knowledge consists in seeing necessary connections between them, which is the function of reason.

Assignment: Read the following text: Science: Conjectures and Refutations" [Hebrew].

Causality refers to the "way of knowing" that one thing causes another. Early philosophers concentrated on conceptual issues and questions. Later philosophers concentrated on more concrete issues and questions. The change in emphasis from conceptual to concrete, i.e. coincides with the rise of empiricism; Hume (1711-76) is probably the first philosopher to posit a wholly empirical definition of causality. Of course, both the definition of "cause" and the "way of knowing" whether X and Y are causally linked have changed significantly over time. Some philosophers deny the existence of "cause" and some philosophers who accept its existence, argue that it can never be known by empirical methods. Modern scientists, on the other hand, define causality in limited contexts (e.g., in a controlled experiment).

Aristotle's Causality: Any discussion of causality begins with Aristotle's Metaphysics. There Aristotle defined four distinct types of cause: the material, formal, efficient, and final types. To illustrate these definitions, think of a vase, made (originally) from clay by a potter, as the "effect" of some "cause," Aristotle would say that clay is the material cause of the vase. The vase's form (vs. some other form that the clay might assume such as a bowl) is its formal cause. The energy invested by the potter is its efficient cause. And finally, the potter's intent is its final cause of the vase. Aristotle's final cause involves a teleological explanation and virtually all modern scientists reject teleology. Nevertheless, for Aristotle, all "effects" are purposeful; every thing comes into existence for some purpose (telos). Modern scientists may also find Aristotle's material and formal causes curious. Can fuel "cause" a fire? Can a mold "cause" an ingot? On the other hand, Aristotle's efficient cause is quite close to what physicists mean by the phrase "X causes Y." Indeed, this causal type ideally suited to modern science. An efficient cause ordinarily has an empirical correlate, for example; X is an event (usually a motion) producing another event, Y (usually another motion). Lacking any similar empirical correlates, material, formal, and (especially) final causes resist all attempts at empirical testing.

Galileo's Causality: Galileo was one of many Enlightenment scientists who wrote explicitly about causality. Galileo viewed cause as the set of necessary and sufficient conditions for an effect. If X and Y are causes of Z, in other words, then Z will occur whenever both X and Y occur; on the other hand, if only X or only Y occurs, then Z will not occur. We can state this more succinctly as "If and only if both X and Y occur, then Z occurs." There is one problem with Galileo's definition. First, the list of causes for any Z would have to include every factor that made even the slightest difference in Z. This list could be so long that it would be impossible to find something that was not a cause of Z. This makes it virtually impossible to tests many causal hypotheses and, so, it makes Galileo's definition practically useless to scientists.

Hume's Causality: David Hume's (1711-76) major philosophical work, A Treatise of Human Nature, lays the foundation for the modern view of causality. Hume rejected the existing rationalist concept of cause, arguing that causality was not a real relationship between two things but, rather, a perception. Accordingly, Hume's definition of causality emphasizes three elements that can verified (albeit post facto) through observation. According to Hume, "X causes Y" if

(1) Precedence: X precedes Y in time.

(2) Contiguity: X and Y are contiguous in space and time.

(3) Constant Conjunction: X and Y always co-occur (or not occur).

At first glance, Hume's definition seems fool-proof. But consider the causal proposition that "day causes night." This proposition satisfies all of Hume's three criteria but, yet, fails to satisfy our common expectation of causality. Day does not cause night and this highlights a potential flaw in Hume's definition. Indeed, each of Hume's three criteria pose special problems for modern scientific method.

Mill's Causality: Unlike earlier philosophers who concentrated on conceptual issues, John Stuart Mill concentrated on the problems of operationalizing causality. Mill argued that causality could not be demonstrated without experimentation. His four general methods for establishing causation are (1) the method of concomitant variation ["Whatever phenomenon varies in any manner, whenever another phenomenon varies in some particular manner, is either a cause or an effect of that phenomenon, or is connected with it through some fact of causation."]; (2) the method of difference ["If an instance in which the phenomenon under investigation occurs and an instance in which it does not occur, have every circumstance in common save one, that one occurring in the former; the circumstances in which alone the two instances differ, is the effect, or the cause, or an indispensable part of the cause of the phenomena."]; (3) the method of residues ["Subduct from any phenomena such part as is known by previous inductions to be the effect of certain antecedents, and the residue of the phenomena is the effect of the remaining antecedents."]; and (4) the method of agreement ["If two or more instances of a phenomena under investigation have only one circumstance in common, the circumstance in which alone all the instances agree, is the cause (or effect) of the given phenomenon."]. All modern experimental designs are based on one or more of these methods. Probabilistic Causality: One approach to the practical problem posed by Hume's constant conjunction criterion is to make the criterion probabilistic. If we let P(Y | X) denote the probability that Y will occur given that X has occurred, then constant conjunction requires that P(Y | X)=1 and P(Y | ~X)=0 where ~X indicates that X has not occurred. The problem, of course, is that biological and social phenomena virtually never satisfy this criterion. Probabilistic causalities address this problem by requiring only that the occurrence of X make the occurrence of Y more probable. In the same notation, if P(Y | X) > P(Y | ~X) then "X causes Y." While this makes the constant conjunction criterion more practical, however, it raises other problems. To illustrate, suppose that X has two effects, Y1 and Y2, and that Y1 precedes Y2. A widely used example is the atmospheric electrical event that causes lightening and thunder. Since we always see lightening (Y1) before we hear thunder (Y2), it appears that "lightening causes thunder. Indeed, Y1 and Y2 satisfy the probabilistic criterion P(Y2 | Y1) > P (Y2) that we require of Y1=>Y2. But in fact, lightening does not cause thunder. The foremost proponent of probabilistic causality, Patrick Suppes, solves this problem by requiring further that Y1 and Y2 have no common cause. As we discover at a later point, research designs constitute a method for ruling out common causes. Design as Operational Causality: The history of causality can be broken into two eras. The first era begins with Aristotle and ends with Hume. The second era begins with John Stuart Mill and continues today. The difference between Hume and Mill may be unclear; after all, both were orthodox empiricists. But while Hume and Mill had much in common, Hume's causality was largely conceptual. Little attention was paid to the practical problem of implementing the concepts. Mill, on the other hand, described exactly how working scientists could implement (or operationalize) his causality. The most influential modern philosophers have followed Mill's example. Although the field of (experimental) design often deals with causality only implicitly, we can think of design as operationalized causality. Rubin Causality: Many proposed causalities work well in one context (or appear to, at least) but not in another. To solve this problem, some modern philosophers have tried to limit their causalities to specific contexts, circumstances, or conditions. Accordingly, Rubin causality (named for Donald B. Rubin) is defined in the limited context of an experimental milieu. Under Rubin causality, any relationship demonstrated in an experiment (where the units of analysis are randomly assigned to experimental and control groups) is a valid causal relationship; any relationship that cannot be demonstrated in an experiment is not causal. To illustrate, suppose that we want to measure the effectiveness of a putative anti-bacterial soap. We apply the soap to a single bacterium. If the bacterium dies, the soap works. But if the bacterium dies, we still have this problem: sooner or later, all bacteria die; maybe this one died of natural causes. We eliminate this (and every other alternative hypothesis) by showing that a placebo treatment does not kill the bacterium. But since the bacterium is already dead, how is this possible? The fundamental dilemma of causality, according to Rubin, is that, if we use an experimental unit (a bacterium, e.g.) to show that "X causes Y," we cannot use that same unit to show that some "non-X does not cause Y." We solve this dilemma by assuming that all units are more or less the same. This allows us to treat one bacterium with the anti-bacterial soap and another with a placebo. To make sure that the two bacteria are virtually indistinguishable, however, we randomly assign the bacteria to the soap and placebo. Since random assignment is unfeasible in some situations, Rubin causality holds that some variables (e.g., "race") cannot be causes. Source: Philosophy of Science on-line

E. Necessity, Sufficiency and Causal Complexity

The main argument of this part of the unit is that researchers interested in diversity, especially as it is manifested in causal complexity, should avoid, as much as possible, making simplifying assumptions about the nature of causation. Specifically, avoid assuming that the individual causes they examine are either necessary or sufficient for the outcomes they study.

While the case study, almost by definition, offers little basis for causal generalization, it has the advantage of providing the investigator intensive knowledge of a case and its history and thus a more in-depth view of causation. Case-study researchers are able to triangulate different kinds of evidence from a variety of different sources in their attempt to construct full and compelling representation of causation. In short, case studies maximize validity in the investigation of casual processes.

While the case study is an excellent research strategy for studying how something comes about, it does not provide a good basis for assessing the generality or the nature of causation the researcher identifies. For example, there is no way to tell if the causes are either necessary or sufficient for the outcome in question. Comparative analysis however may be more useful here.

Yet, social scientists have been slow to recognize that different analytic strategies are relevant to the assessment of different kinds of causes. At the most basic level, it is important to recognize that the study of necessity works backwards from instances of an outcome and is search for common antecedent conditions. The study of sufficiency, by contrast, works forward from instances of a causal conditions to see if these instances agree in displaying the outcome.

If, indeed, the most common form of social causation involves causes that are neither necessary nor sufficient, then the assessment of the cross-tabulation of a single cause with the outcome in questions provides little useful information. Instead, as I show in the next section, the investigator should cross-tabulate the outcome against combinations of causes. This shift in analytical strategy is the first step on the road to the analysis of causal complexity, defined here as a situation where no single cause is either necessary or sufficient.