People of lower socio-economic status (SES) appear to always have much worse health outcomes. At least until the end of life, at each age every movement down in income is associated with being in poorer health. While a debate rages on about competing reasons why SES may affect health, there is little recognition that the so-called reverse causation from health to economic status may be pretty fundamental as well. Even if the direction of causation is that SES mainly affects health, what dimensions of SES actually matter — the financial aspects such as income or wealth or non-financial dimensions like education? Finally, is there a life course component to the health gradient so that we may be mislead in trying to answer these questions by only looking at people of a certain age — say those past 50. This paper, which is divided into four sections, provides my answers to these questions. The first section examines the issue of reverse causation or whether a new health event has a significant impact on four dimensions of SES-out-of-pocket medical expenses, labor supply, household income, and household wealth. The next section switches the perspective by asking whether the so-called direct causation from SES to health really matters all that much. If the answer is yes and it will be, a sub-theme in this section concerns which dimensions of SES- income, wealth, or education-matter for individual health. Since the answer to that question turns out to be education, Section 3 deals with the very much more difficult issue of why education matters so much. The evidence in these first three sections relies on data for people above age 50. In the final section of the paper, I test the robustness of my answers to these basic questions of the meaning of the SES-health gradient using data that span the entire life-course.