What is wealth? Let me try a slightly non-standard answer to that question. Wealth is a measure of your ability to do what you would like to do, when you would like to do it - a measure of your breadth of immediately available choice. Therefore your wealth is determined by the resources you presently own, as everything requires resources.
For the sake of argument, let us say that your resources presently amount to a leather bag containing a hundred unmarked silver coins. Interestingly enough, by the "what would you like to do" measure, you are fantastically more wealthy than any given ancestor put in the same position of ownership. You have immensely greater choice. Clearly there is more to wealth-as-choice than present property. We must also consider the historical investment made into increasing choice, and into lowering the cost of specific - usually popular - choices. The engines of technology and open, free markets are turned by people to create new, better, cheaper choices. The choice to fly, the choice to remain alive with heart disease, the choice to avoid that heart disease.
Where do silver coins - or indeed, any other resources you might own - come from? Where does investment come from? After all, we don't come into this world with the proverbial silver implement between the teeth. No, we worked for those coins. We spent time and negotiated payment for that time. Why? Because time is valuable.
But time spent alive, measured in the ticking of heartbeats, is more than valuable - it is wealth itself, the source of all other measures of wealth. All property was created by someone, somewhere, taking their time. The creation and exchange of property is a way to make time fungible, transferrable, a more valuable resource. Time spent alive is the root of all property, all human action, and thus all wealth - both the silver in your pocket that provides for present choice, and the wealth of possible choices created by past investment.
Time is everything. How much have time you spent reading this far? Could you have been doing something more useful, more optimal from your perspective? We make these small evaluations constantly, because time is the most valuable thing we have.
We all go through engineering our cycles of property and time; how can we best optimize time to generate property that can be used to make our time more effective? We do this in small ways and large, but everyone does it. Some people do it so effectively they launch themselves into property escape velocity, exponentially increasing the effectiveness of their time and exploring the outer limits of what it means to maintain ownership of a great deal of property.
Interestingly, despite the grand importance of time as the absolute foundation of wealth, very little progress has been made in the most obvious optimization of all: creating property that can create more time. More heartbeats, more health, more time spent alive and active. Rejuvenation medicine, capable of repairing the damage of aging. Tissue engineering to generate replacements for worn organs. The cure for cancer. If you could do all that, then the much more productive form of escape velocity becomes possible - longevity escape velocity. Why strive to maintain an empire of property that will crumble to dust when the degenerations of age catch up with you when you could be that fit-looking guy having a blast swimming in the breakers every other Sunday for as long as you like?