Argueing: are true facts enough ?
The Stone is featuring occasional posts by Gary Gutting, a professor of philosophy at the University of Notre Dame, that apply critical thinking to information and events that have appeared in the news.
In trying to cut through the passion and rhetoric of political debates, one important move is to focus on the facts relevant to the issue in dispute. This, however, is not as easy as it might seem. To make the issues concrete, consider an example from current discussions of the federal budget.
Even a strong argument from purely factual premises is open to refutation unless it takes into account all relevant facts.
John Taylor, a distinguished economist at Stanford, recently wrote a column in the Wall Street Journal in which he offered a "fact-based" critique of President Obama's budget proposal. The centerpiece of his argument was a chart showing the amount of federal government expenditures from 2000 to the present, along with projections of what Obama proposes to spend from now through 2021. According to the chart, in 2000 spending was 18.2 percent of our gross domestic product and has steadily increased, reaching 19.6 percent in 2007, and averaging 24.4 percent for the last three years. Obama's budget slightly reduces this rate to about 23 percent over its first few years, but then gradually increases it, ending with a rate of over 24 percent in 2021.
The argument could be pursued much further, but this is enough for my purpose, which is not to argue about the budget but to reflect on difficulties involved in arguing from the facts. The key point is that both Taylor's argument and that of his critics were based on established facts. Moreover, in each case, the facts did support the conclusions Taylor and his critics were arguing for. There was no flaw in their logical moves from premises to conclusions. How, then, could there be something wrong with their arguments?
The answer lies in a crucial distinction between deductive and inductive reasoning. In a deduction (e.g., all humans are mortal; Socrates is human; therefore, Socrates is mortal), the truth of the premises logically requires the truth of the conclusion. If the premises are true, the conclusion must be true. Adding further premises that might seem relevant to the conclusion (e.g., Socrates is very young and there will be major medical advances before Socrates reaches old age) will make no difference to the conclusion.
In an inductive argument (e.g., Most humans do not live for 100 years; Socrates is human; therefore, Socrates will not live for 100 years), the premises only make the conclusion probable. As a result, adding further premises can alter the force of the argument. For example, if Socrates is 99 years old and in very good health, it is probable that he will live to be 100.