Gematria, in full
The starting point is a plain historical fact rather than a claim. Hebrew had no separate digits, so its letters carried numeric duty: the first nine letters run 1 to 9, the next nine run 10 to 90, and the last four run 100, 200, 300 and 400. Anyone writing a date or a quantity used letters to do it. Reading a word's total is therefore not an imposition on the script, it is an available property of a script that was already a numeral system.
Interpretive use of those totals is documented in antiquity and elaborated at length in later rabbinic and Kabbalistic writing, where an equal total between two words or phrases is treated as an invitation to read them together. Letters had already been doing numeric duty in Babylonian and Greek writing, and the Greek version of the practice has its own name, isopsephy, which turns up in literary contexts and in graffiti. Arabic has the abjad system, in which the letters are ordered into an older Semitic sequence for numeric use.
The difference from modern numerology is worth keeping sharp. Gematria operates on a numeral system that people genuinely used, applied to fixed texts in their original language, and its history can be traced through surviving documents. Modern numerology applies a chart invented in the twentieth century to the Latin alphabet, and to birth dates and personal names rather than scripture. The mechanics rhyme. The provenance does not, and conflating the two overstates the age of one and understates the documentation behind the other.
- Numerology
- Hebrew numerology
A worked example
The Hebrew word chai, meaning life, is written with chet and yod, worth 8 and 10, so it totals 18. Gifts and charitable donations in multiples of 18 are a widespread living custom that follows straight from that sum, which is why cheques for 36 and 180 turn up at weddings. The number is doing the same work a word would, and everyone involved knows the arithmetic.
Sources
Each of the 22 Hebrew letters carries a numeric value, running 1 to 9, then 10 to 90, then 100 to 400, and letters were used as numerals by the Babylonians and the Greeks as well.
Jewish Virtual Library — GematriaThe Hebrew word chai is written with the letters chet and yod, whose numerical values add up to 18.
My Jewish Learning — Chai
See also
Where it comes up on this site
Gematria: frequently asked
No. Gematria works on Hebrew letters that genuinely served as numerals. Modern numerology applies a twentieth-century chart to the Latin alphabet. They share a technique and very little else.
Chai, life, is spelled chet plus yod, worth 8 and 10. Giving in multiples of 18 followed from that sum and became a durable custom.
Greek has isopsephy and Arabic has the abjad system. Both come from the same situation: alphabets doing double duty before separate digits were adopted.