Final answer:
To qualify for Social Security disability benefits, an individual must be unable to perform any substantial gainful activity due to a disabling condition expected to last at least twelve months or result in death, not simply unable to perform their usual job duties or qualify for other disability insurance.
Step-by-step explanation:
To qualify for Social Security disability benefits, an individual must be unable to perform any substantial gainful activity due to physical or mental impairment. This impairment must be expected to last at least twelve months or result in death. The focus is not on whether the individual can perform their customary duties, or on their eligibility for other insurance plans, but rather on the severity and expected duration of their disability. It is important to consider that conditions that can be mitigated by medical devices or controlled by medication may not qualify as disabilities under Social Security's definition.
Supplemental Security Income (SSI) is another program that provides income to individuals who have a disability and meet certain income thresholds. Social Security is essential as it serves as a significant source of income for many Americans, especially the elderly, and helps prevent poverty among retirees and disabled individuals.