The canons of taxation were first introduced by Adam Smith, who was a renowned economist. These canons provide the principles which should be followed while designing a tax system. According to Adam Smith, tax systems should adhere to four canons - equity, certainty, convenience, and fiscal adequacy.

Equity, which is also known as fairness, means that the tax burden should be distributed in a way that takes into consideration the ability of individuals to pay taxes. This ensures that individuals with higher incomes pay a higher proportion of taxes.

Certainty means that taxpayers should have a clear understanding of how much tax they are required to pay and when it is due. This helps in avoiding confusion and uncertainty.

Convenience means that the tax system should be designed in a way that is simple and convenient for taxpayers to comply with. This can include features such as easy-to-understand tax forms and simplified procedures.

Fiscal adequacy means that the tax system should generate enough revenue to meet the financial needs of the government.

The correct answer to the question is option 4 - Canon of fiscal adequacy. This is because Adam Smith did advocate for a tax system that generates enough revenue to meet the government`s financial needs. Therefore, option 4 is the one canon of taxation that was not advocated