The Spirit of the Tarot
The Search for God's Picturebook

The first card of the  fifth suit in  the Tarot of Marseilles depicts a jester called the “Fool.” It is unnumbered. The other 21 cards are clearly labeled with Roman numerals. In the Roman system of numbering there is no zero (the concept was brought to Europe from India by the Arabs). All numbers were thought of as emerging out of the fullness of number one. Therefore, the fool is not zero; he is simply outside the series.

Robert M. Place, The Buddha Tarot: A Mandala of Cards, REDFeather, 2021, p 111.