Assignment: Defining Types of Causation
In this week's reading we learned about four types of causality: causally necessary, causally sufficient, causally necessary and sufficient, and causal dependence of one variable on another.
Supply two example claims of at least two types of causality and label them appropriately. Then, explain why the example fits your definition/selected type of causality.
The first kind of cause is a necessary cause, or causally necessary condition. A necessary cause for an effect E is a condition which is needed to produce E. If C is a necessary cause for E, then E will never occur without C, though perhaps C can occur without E. For example, the tuberculosis bacillus is a necessary cause of the disease tuberculosis. Tuberculosis never occurs without the bacillus, but the bacillus may be present in people who do not have the disease.
A given effect may have several necessary causes. Fire, for example, requires for its production three causally necessary conditions: fuel, oxygen (or some similar substance), and heat.
The second kind of cause is a sufficient cause, or causally sufficient condition. A condition C is a sufficient cause for an effect E if the presence of C invariably produces E. If C is a sufficient cause for E, then C will never occur without E, though there may be cases in which E occurs without C. For example (with respect to higher animal species), decapitation is a sufficient cause for death. Whenever decapitation occurs, death occurs. But the converse does not hold; other causes besides decapitation may result in death.
A given effect may have several sufficient causes. In addition to decapitation, as just noted, there are many sufficient causes for death: boiling in oil, crushing, vaporization, prolonged deprivation of food, water, or oxygen-to name only a few of the unpleasant alternatives.
Some conditions are both necessary and sufficient causes of a given effect. That is, the effect never occurs without the cause nor the cause without the effect. This is the third kind of causal relationship. For example, the presence of a massive body is causally necessary and sufficient for the presence of a gravitational field. Without mass, no gravitational field can exist. With it, there cannot fail to be a gravitational field. (This does not mean, of course, that one must experience the gravitational field. Moving in certain trajectories relative to the field will produce weightlessness, but the field is still there.)
The fourth kind of causal relation we shall discuss is causal dependence of one variable quantity on another. A variable quantity B is causally dependent on a second variable quantity A if a change in A always produces a corresponding change in B. For example, the apparent brightness B of a luminous object varies inversely with the square of the distance from that object, so that B is a variable quantity causally dependent on distance. We can cause an object to appear more or less bright by varying its distance from us.
An effect (such as apparent brightness) may be causally correlated with more than one quantity. If the object whose apparent brightness we are investigating is a gas flame, its apparent brightness will also depend on the amount of fuel and oxygen available to it, and on other factors as well.