In 1494, Luca Pacioli, a Franciscan Friar and eminent mathematician, wrote a treatise on the double entry system in use in Venice. He was the first person to record it and that is why he is called ‘The Father of Accounting’, though he wasn’t even an accountant at all!
The system he described was (and is) based on these three premises:
Pacioli deduced:
This explains why assets and expenses are dealt with in the same way in the double entry system; it is because they are both on the same side of the equation. The same is true of liabilities and revenues; they too are on just one (the same) side of the equation.
This topic is dealt with in more detail in chapter ten of ‘Understand Accounting’.
I have developed Pacioli's approach in two papers that were published in 'De Computis' in 2021 and 2022.