Medieval Scholars had started to introduce some economic problems along with their solution. Among of them wrote on money, earning, taxation, behaviour in consumption, etc. Al-Ghazali, for instance, was famous with his theory of money. He reiterated that money must, at least, cover three functions. First of all, store of value. Secondly, as unit of account. Thirdly, as unit of measurement. In that case, the gold and silver are the most reliable metal to become money.
The reason behind that is because all people in this world surely accept these both intricts values in whatever their shape are. In contrast with paper money, which is only acceptable due to central bank (government) authority that convince the people that this money can be used for economic transactions. As a result, more people now sell their gold to get their paper money. In addition, paper money can be only accepted in certain countries where it was printed. Malaysian Ringgit never be acceptable as currency and cannot be used outside Malaysia. Likewise Rupiah, people in the USA don’t accept it as their currency.
Based on these facts above, I then conclude that the current money we use now has nothing in term of its value. It is merely a piece of paper that authorized by the Central Bank. The moment the central bank disagree with its guarantee upon paper money, we lost our wealth we’ve spent our life earning them.