Immigration reform is a hot topic and has been for at least the last 10 years, which covers the time that I have been paying attention to it. One of the things I have noticed when I discuss immigration with other people is their desire to make general statements about immigrants, particularly immigrants from Mexico, based on their own experiences. This type of reasoning is inductive reasoning as opposed to deductive reasoning.
Inductive reasoning can be useful. Drawing on personal experiences when discussing larger topics is something that we all do and often is useful for moving a discussion forward. But inductive reasoning does not establish truth. It can only provide evidence that the more general statement that follows from the premise is possible with varying degrees of certainty. The degree of certainty depends on the strength of the premise and other evidence.
In the context of immigration, an inductive argument I hear a lot is of the type:
"All illegal Mexican immigrants I have heard of or have interacted with are only in the U.S. to mooch off of our social safety net. Therefore, all illegal Mexican immigrants are probably here to mooch off of our safety net rather than work."
The premise, that Mexican immigrants are in the U.S. to take advantage of our welfare programs, is based on a limited sample size, namely what the person has read about or seen. The conclusion, that all Mexican immigrants are probably identical to the sample in the premise, extrapolates what the person has experienced into a general statement about an entire group of people. Note that the conclusion may or may not be true; the argument itself does not establish truth.
Deductive reasoning starts from a principle that has been established as truth (or is at least widely believed to be true) and then logically works towards a second truth. A conclusion based on a correctly specified and coherent deductive argument is necessarily true.
For example, a deductive reasoning example of thinking about Mexican immigrants could be:
"People want to obtain the things that they desire at the least possible cost, where costs include not only pecuniary costs but also time, effort, and hardship. Therefore, illegal Mexican immigrants that come to the U.S. and take advantage of our welfare program will only do so if it is the least costly way of obtaining the goods and services that they desire."
Rather than assume that Mexican immigrants are here to mooch off of U.S. taxpayers, the argument above assumes that they respond to incentives, which is more certain. When the argument is presented this way it is more clear where solutions to the welfare problem may be found.
If we raise the relative cost or lower the benefit of being on welfare, less Mexican immigrants would see it as the solution to their economic problem. One way to do this is to make it easier to obtain a green card so that more immigrants can work legally. This lowers the cost of work relative to that of hiding out illegally and mooching off the system. If illegal Mexican immigrants could come out of the shadow economy and get legal permission to work they would be more likely do so. As it stands now, to the extent that they mooch of the system, it is because it is less costly for them to hide underground, draining local resources such as public schools, local hospitals, food banks, churches, local welfare programs, etc. without contributing any tax dollars or donations to the upkeep of such services.
I try to avoid inductive reasoning when possible but like anyone I rely on my own experiences and observations to make sense of the world. Inductive reasoning is not bad, but when a person uses it they should be sure to acknowledge to both themselves and others that their conclusion is only a possibility rather than a certainty. If it is truth that is being sought, deductive reasoning is the only way to get there. And even if the truth proves difficult to get at, deductive reasoning often provides a better framework for analyzing the situation.