larger denominations were intended for major expenditure. The same
kinds of agreements must also have existed with the Macedonian king-
dom. We simply do not have an equivalent commercial agreement.^9
One of the difficulties in trying to understand the changing nature of
economic interactions is the difficulty of distinguishing between broad,
quasi-evolutionary patterns of behaviour, with different agents gradually
adapting their ways of doing exchange in response to wider practices,
and significant events that had a marked impact on these processes. We
do not know, for example, whether the Athenian agents in the Helle-
spontine region, theHellespontophylakes, adopted a shrewd policy of
taxing ships passing through the Straits soon after the Delian League was
formed in 479bc, or whether this was a somewhat later response to
observations of commercial traffic. Rubel believes that the imposition of
a two per cent tax could have begun as early as the 470sbc.^10 This
question is connected to broader ones about how the Delian League
operated over the course of the two middle quarters of thefifth century
bc. Scholarly perceptions of the economic and political effects of this
union have changed quite markedly over a century of research.^11 The
economic role of the Straits, in the fourth and third centuriesbcin
particular, becomes easier to comprehend when we include in any
putative scenario what was happening on the landward, European and
Asiatic shores, as well as at sea. The narrative of Byzantine expansion
makes better sense if we allow for a wider range of processes that affected
events in the Bosporus. In principle, these processes could be traced
further, in a series of infinitely regressing acts, with factors further afield
having some impact on events along the coast, like waves moving
progressively towards the sand. In practice, it may be more straightfor-
ward to adopt the concept of‘boundary conditions’, a tool used by
mathematicians and scientists to determine the circumstances in which
certain values are considered to be valid.^12 This is not an attempt to
introduce a false, mechanistic model into our thinking about economic
processes. On the contrary, the concept of‘boundary conditions’is here
conceived as a purely abstract, heuristic device, to help re-imagine what
(^9) The agreement between Amyntas III for the Macedonian crown and the Amphipo-
litans, Bottiaians, Akanthians, and Mendaeans (RO 12), shows the same kinds of bilaterial
mechanisms in operation as in the Pistiros inscription, with the ruler representing one half
of the agreement, with the other signatories as recipients of privileged access to timber
resources in this case.
(^10) Rubel 2001, 49.
(^11) See esp. the contributions to Ma et al. 2009, for a wide-ranging review.
(^12) Boundary conditions: http://www.mathworld.wolfram.com/BoundaryConditions.html.
The lure of the northern Aegean 253