Di Tian Sui (滴天髓) — Drops from Heaven's Marrow

Di Tian Sui (滴天髓, literally "Drops from Heaven's Marrow") is widely regarded as the most important classical text in the BaZi tradition. Written in verse form, attributed to a scholar of the Yuan dynasty and significantly expanded by commentators in the Ming and Qing periods, it covers the core theory of Four Pillars reading — particularly the assessment of chart strength and the selection of the useful god.

The Text and Its Commentaries

The original Di Tian Sui consists of rhyming verse passages — each a condensed principle of BaZi theory. Because the verses are intentionally cryptic, they require commentaries to be understood. The most influential commentaries are those of Ren Tiechiao (任铁樵) of the Qing dynasty, who supplemented each verse with extensive case studies and explanations, and Chen Su'an, whose more accessible modern commentary introduced Di Tian Sui to a wider audience.

Core Teachings

Di Tian Sui's central contribution to BaZi theory is its systematic treatment of chart strength (身强弱) and the selection of the useful god (喜用神). Key principles include:

• Month令 is paramount — the month branch's seasonal authority (月令) is the single most important factor in determining chart strength. No other pillar overrides it.
• The useful god determines life themes — identifying the element the chart most needs, and tracking when it arrives, is the primary tool of timing analysis.
• Strength must be assessed before Ten Gods — the meaning of any Ten God changes based on whether the Day Master is strong or weak. An Officer that challenges a weak chart harms it; one that challenges a strong chart structures it.
• Special chart formations — Di Tian Sui documents cases where a Day Master that appears to have no support actually "follows" the dominant force, creating follow-the-strength charts (从格) with their own rules.

The Five Periods of Verse

The text is traditionally divided into sections covering: Heaven and Earth (Tian Di 天地 — the stems and branches as cosmic forces), the nature of each heavenly stem, the assessment of the five element groups, the reading of the Day Master, and the analysis of special and follow charts. Each section builds on the previous, creating a complete framework for chart analysis.

Influence on Modern BaZi

Di Tian Sui's framework — particularly its emphasis on chart strength as the primary lens — became the dominant approach to BaZi through the 20th century, especially in Taiwan, Hong Kong and Singapore. Most modern BaZi practitioners, whether they have read the text directly or not, work within a framework derived from Di Tian Sui's core principles.