A) Inspiration:
1."Does causality involve contiguity"-from Mario Bunge in his book: "Causality and Modern Science"
2. Torsten Hägerstrand and his Time Geography
B) Context: urban sprawl/spatial multipliers
C) Main assumption: the central business district is known and is stable in time and geographic space
D) Question breakdown: Can the trajectory of urban growth be determined (e.g. centrifugal forces radiating from the CBD) if patterns of spatial contiguity are identifiable?
E) Empirical source: spatial contiguity is analyzed through images of the land mass (e.g. remotely-accessed).
http://www.amazon.com/Causality-Modern-Science-Revised-Edition/dp/0486237281
http://en.wikipedia.org/wiki/Time_geography
Generally speaking, contiguity is symmetrical, whereas causality is oriented (asymmetrical), so, to start with, wouldn't you require contiguity plus an element of direction to consider an equivalence with causality ? This element could be for instance precedence in time (which is oriented).
Applying to urban growth, my take would be that contiguity is an indicator, a result of urban growth. Additionally, urban density, hence urban growth, is an arbitrary threshold of density, so an imperfect marker of actual contiguity. The causes of urban growth are multiple (and can be endogenous), but in a nutshell proximity (or contiguity) is caused by agents' socio-economic decisions. Existing urban locations are a moderator of urban growth (through market signalling). For example, economic growth is the cause of the creation of new firm establishments. Real estate (and other) prices act as a signal for firms to choose to locate establishments at a certain distance from existing locations (as close as economies of proximity call for). Urban contiguity then results (or not).
From a high altitude, it may look like organic tissue growth, or cell division, but the causal mechanisms are actually of a socio-economic nature, and seen up close contiguity is relative/arbitrary, unlike organic connective tissue which is topologically continuous.
Hi Sylvain,
Thanks for highlighting assumptions and premises that need further refinement. I think that your answers are robust and well-developed.
Regards,
Bernard
No, not generally, contiguity does not imply causality. This is quite context dependent, and even then it doesn't necessarily imply causality. In urban growth, cities do tend to expand into adjacent areas, making a contiguous area, but this doesn't have to be the case. The Denver airport in Colorado comes to mind: really far from the contiguous developed area of Denver! Topographic considerations (e.g., mountainous terrain, water infrastructure feasibility, etc.) can constrain this expansion pattern too. But there are cases in which it would be spurious to call contiguity a symptom of cause; say two cities with very different economic histories eventually coalesce over time to become contiguous.
Hi Paulo,
Very fascinating views and observation. I especially like the case for a hypothesis test suggested in:"say two cities with very different economic histories eventually coalesce over time to become contiguous" Reminds me of Budapest, Hungary. Consisting of three separate historic cities: Buda, Pest and Óbuda united in jurisdiction/by decree- so that causality cannot be determined purely on grounds of contiguity.
Best Regards,
Bernard
It's important to note that the "third revised edition" of Mario Bunge's book was published in 1979, and is simply a slightly revised version of the second (1963) edition. The philosophy of causation has come a long way since then; two major works are Wesley Salmon, Causality and explanation. New York, NY: Oxford University Press (1998), and Nancy Cartwright, Hunting causes and using them. Cambridge, UK: Cambridge University Press (2007). See the attached paper for a more extensive bibliography and a discussion of the methods that can be used to demonstrate causation.
Hi Joseph,
Thanks for the links and the update on the "state-of-the-art"
Cheers,
Bernard
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