Here is a good history of the SS system.
It describes the current system this way:
*The “New” Alternative
With the coming to office of President Roosevelt in 1932, and the introduction of his economic security proposal based on social insurance rather than welfare assistance, the debate changed. It was no longer a choice between radical changes and old approaches that no longer worked. The “new” idea of social insurance, which was already widespread in Europe, would become an innovative alternative.
Social insurance, as conceived by President Roosevelt, would address the permanent problem of economic security for the elderly by creating a work-related, contributory system in which workers would provide for their own future economic security through taxes paid while employed. Thus it was an alternative both to reliance on welfare and to radical changes in our capitalist system. In the context of its time, it can be seen as a conservative, yet activist, response to the challenges of the Depression.*"
It also suggests that:
*The two major provisions relating to the elderly were Title I- Grants to States for Old-Age Assistance, which supported state welfare programs for the aged, and Title II-Federal Old-Age Benefits. It was Title II that was the new social insurance program we now think of as Social Security. In the original Act benefits were to be paid only to the primary worker when he/she retired at age 65. Benefits were to be based on payroll tax contributions that the worker made during his/her working life. Taxes would first be collected in 1937 and monthly benefits would begin in 1942. (Under amendments passed in 1939, payments were advanced to 1940.)
The significance of the new social insurance program was that it sought to address the long-range problem of economic security for the aged through a contributory system in which the workers themselves contributed to their own future retirement benefit by making regular payments into a joint fund. It was thus distinct from the welfare benefits provided under Title I of the Act and from the various state “old-age pensions.” As President Roosevelt conceived of the Act, Title I was to be a temporary “relief” program that would eventually disappear as more people were able to obtain retirement income through the contributory system. The new social insurance system was also a very moderate alternative to the radical calls to action that were so common in the America of the 1930s.*
Finally, it suggests this:
From 1937 until 1940, Social Security paid benefits in the form of a single, lump-sum payment. The purpose of these one-time payments was to provide some “payback” to those people who contributed to the program but would not participate long enough to be vested for monthly benefits. Under the 1935 law, monthly benefits were to begin in 1942, with the period 1937-1942 used both to build up the Trust Funds and to provide a minimum period for participation in order to qualify for monthly benefits.
There’s lot;s more stuff in there. It really is quite interesting. One thing to note regarding the removal of caps (as SteveMB did) is that the system currently works such that larger benifits are paid if you have contributed more. They are also adjusted, however, such that a larger proportion of your income is replaced if you are lower on the economic ladder. So, SS does both. It provides welfare to the indigent elderly, AND it provides a self financed retirmement insurance benifit to more productive members of society.
Anyway, I just wanted to introduce that article.