In the grid system, the dimensions or axes of the grid -- the rows and columns -- are different known series, be they numerical, alphabetical, or whatever. If each cell has a row letter and a column number, that two-character combination becomes a hook for the mental image that goes in the cell. Each mental image simply incorporates the code for that cell.

This was essentially how the memory masters of the Renaissance -- men like Giordano Bruno -- worked to store and encode vast amounts of knowledge. They typically were intimately familiar with many list-like sequences to which cell rows and columns could be keyed – the zodiac, pantheons of classical deities, Biblical genealogies, etc. These things came readimade with vivid associations to help in fashioning memory images, although theoretically a memory grid could be constructed using simple number- and alphabet codes.

It is possible to create vast mental spreadsheets using this method. And the only limit to the number of dimensions of such a system would how many natural series of things you can use for coding. There’s the alphabet – a series 26 items long that almost everyone knows by heart – and the numbers; even just using the digits 0-9 (or 1-10) plus the alphabet gives you a grid with 260 cells – more than I’ve ever needed (but I’ve never needed to memorize a book). Multiply that by the 12 months of the year and … well, you get the idea.

NEXT PAGE: Economy Is the Soul of Memory