Deductive Argument
In formal logic, arguments will be considered as deductively valid where the conclusion is drawn is true without a doubt, if the premises on which the conclusion is based are true. Arguments are considered inductively strong when the conclusions can be drawn on the probability of the premises being true. When the premises are secured and can be considered valid and true it is possible to derive a deductive logic from which the desired conclusion necessarily follows. Even though it is rare to have certainty with respect to any premises, in medical science it is desirable to have deductive logic for making decisions. However, it is not possible to avoid certain inductive conclusions due to the nature of various problems faced in the profession of healthcare. From the discussion, it follows that a deductive argument is one in which the premises are intended to provide absolute support for a conclusion. On the other hand, in the case of inductive argument, the premises can be expected to provide support for a conclusion only to some extent (Jenicek, 2003).
In the profession of healthcare, deductive and inductive logic are not used in their perspective of true logical sense. The terms are used in the process of reasoning itself. In epidemiology, deductive reasoning is used as a starting point for the gathering, analysis and interpretation of data. It involves using a general principle or hypothesis, which will be confirmed or refuted based on the analysis and interpretation of the information and data collected. Therefore, the relationship between the evidence on the grounds for the inference and the inference by itself can only be true if the underlying premises are true. Even when the premises on which the decision is based are inaccurate, still the conclusion might be true (Jenicek, 2003).
Example
An example for deductive reasoning is (that is drawing a necessary conclusion)
- Alcoholic patients vomiting fresh blood have esophageal ruptures (General)
- The patient who vomited fresh blood is an alcoholic (specific)
- Because the patient vomited fresh blood and those patients vomit fresh blood have esophageal ruptures this patient also has ruptured esophageal varices. (specific)
Inductive Argument
Inductive reasoning on the other hand makes use of established facts for drawing general conclusions or for confirming or refuting a hypothesis. Therefore, inferences or conclusions, which are just probable and not confirmed as true are known as inductive inferences or inductive arguments. Here the conclusion or the inference might still be false even if the evidence or premises on which the decision is based are accurate and true. In the case of inductive reasoning, the inference is only probable.
Example
An example for inductive reasoning is (that is drawing a probable conclusion)
- Alcoholic patient A who vomited fresh blood is known for having esophageal ruptures
- Alcoholic patient B who vomited fresh blood is known for having esophageal ruptures
- Therefore, alcoholic patients who vomit fresh blood have esophageal ruptures.
Normally, professionals in healthcare services do not try to generalize beyond the basic argument of “alcoholic patients who vomit fresh blood bleed from ruptured esophageal varices (Or, patients bleeding from ruptured esophageal varices are alcoholics)” (Jenicek, 2003). Such generalizations are not normally accepted as valid by the logicians; but are accepted in the healthcare profession.
References
Jenicek, M. (2003). Foundations of Evidence -based Medicine. New York: Informa Healthcare.