The picture that emerges from descriptions by ancient writers, particularly Demosthenes, underlines the economic importance of banks; the risk involved in their activities; and their hidden sources of capital. Nothing in the Athenian economy was straightforward! Only a handful of things could be placed chronologically with certainty, and still fewer could become known to the general public.

The bank played its part by putting up credit in the shape of maritime loans. This was very important for the financing of sea trade - a crucial sector for a society based, as Athens was, on imported grain. Via the bank, the identity of the depositors - particularly those whose invisible incomes financed maritime loans - was kept a secret. It was precisely because bankers were noted for their high moral fibre, that they were able to acquire large sums of cash and put them to work.

Sometimes it became necessary for a payment to be made in secret so that a political disagreement could be settled, or so that an indictment could be dealt with discreetly. It was often the banks that provided funds, with no names attached. Bank operations were connected, in the mind of the simple citizen, with hugger-mugger. Of course this was helped by the fact that the banks were the only form of trading where no witness was required. As a rule bankers kept written records of their dealings, but there were cases where transactions were kept hidden even from these.
Every so often an activity of this kind would come to light. One of the great causes celebres was in the period 386-7-354 B.C., when the sacred Opisthodomos of the Acropolis was set on fire by the treasury officials of the god Athena. This was an attempt to avoid discovery of secret loans of public money to banks. The money (one must assume) remained untouched and was the responsibility of the treasury officials. The banks being in no position to repay the loans in question, the treasurers resorted to arson in a fruitless attempt to cover their tracks. The ensuign investigation brought their breach of the law to light, and as a result they went to jail. The whole business strengthened the general impression that banking mechanisms were intimately linked with the invisible economy.