When is a tax not a tax? When it's a contribution-or-when it's an insurance premium. This is the situation wherein one is gainfully employed and is required, along with the employer, to pay into a trust fund from which he will receive future Social Security benefits-out of current wages and employer chip ins. The legislation dates from FDR's New Dealand it's called FICA-Federal Insurance Contribution Act (note the nine-letter word "insurance").
The above is prologue to the argument over whether those who don't pay any federal income tax, but do pay their FICA premiums, are actually legitimate taxpayers.
As a generalization, I might observe that folks of a lLeft-leaning mind-set insist that FICA-payers are real taxpayers, while folks of a right-leaning mind-set are more likely to argue that-when the legislation mandating the payment specifically calls the future-pay-out program insurance-it is indeed an insurance premium and not a tax.
This is more than an argument over whether a non-quacking duck is still a duck; it goes to the question of the percentage of U.S. citizens who enjoy all governmental services without paying for them. That, in turn, is relevant because it goes to the question of innate human behavior, and whether people who are shielded from paying for any government service are more inclined to vote for more of it than those who aren't so shielded. (Think Act 60 and Son-of-60, 68, and the income-sensitivity provision of the property-tax program which funds the public schools; well over half of Vermont homeowners are shielded from paying the full costs of school-budget growth they have been voting for.)
People who think and write about such things have recognized the problem-from philosopher Plato to politico Ari Fleischer. Fleischer recently (April 13 had an oped in the Wall Street Journal entitled "Everyone Should Pay Income Taxes"). The Middlebury College alumnus' thesis focused on the adverse effects on the overall economy (supported only by actual taxpayers) of the pro-spending voting tendencies of non-taxpayers.