The Dictionary of Human Geography

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studies, became increasingly important.

Vigorous geographical debates were also

stimulated bypost-colonialismand concern

with sexual liberation (seesexualityandqueer

theory), as issues ofcultural politicscame

to the fore, with each of these approaches being

connected with political struggles inside as well

as outside the academy (Blunt and Wills,

2000). In an editorial marking the twenty-fifth

anniversary ofAntipode, Walker and McDowell

(1993, pp. 2–3) signalled this diversity, argu-

ing: ‘No single oppression or axis of social

life can be treated as merely secondary or an

afterthought of radical research or politics.

Whilesocialismand Marxism remain central

to the vocabulary of the Left, we hold to no one

orthodox view of radical analysis.’

Radical approaches have become increas-

ingly accepted and influential in the discipline,

yet much of the earlier optimism about the

prospects for fundamental social change has

receded. The idea of a ‘common vision’ or

project in geography has also been challenged.

Some have welcomed the pluralization of the

Left, but others have worried about its frag-

mentation and depoliticization, asserting that

while it is necessary to recognize the diversity

of current struggles, it is also important to find

points of commonality and unity between

them in order to enable political change.

Many now employ the termcritical human

geographyas a related and looser label for

ideas and practices committed to an emanci-

patory politics, and considerable discussion

has recently centred on the effects of institu-

tionalization and professionalization within

the academy as well as on political commit-

ment, onactivismand on different ways of

contributing to progressive social change

(including through debates inAntipodeabout

‘what’s left?’; see also Castree, 2000). Initiatives

such as the conferences of the International

Critical Geography Group and the develop-

ment ofinternetforums are providing new

means for developing and debating radical

perspectives, and for connecting different

forms of radical geography, which have their

own geographies and histories. Radical per-

spectives in geography are further being gal-

vanized by current political struggles against

capitalism, imperialism,warand other forms

of oppression that underline the continuing

need for approaches that provide ‘[d]issentient

thoughts and norm challenging information’,

and that are prepared ‘to bring the undis-

cussed into discussion; to stray beyond estab-

lished perimeters of opinion; to render the

familiar not only strange but, often-times,

unacceptable; and to explore the depths of

the meaning of ‘‘radical’’ itself as a conceptual

rubric’ (Castree and Wright, 2005, p. 2). dp

Suggested reading

Blunt and Wills (2000); Peet (1977, 2000).

rank-size rule An empirical regularity iden-

tified in the city-size distributions of some

countries and regions. Generally, if the cities

are ranked from 1 (the largest) ton(the smal-

lest), then the population of any city –k– can

be determined from the equation:

Pk¼P 1 =k,

whereP 1 is the population of the largest city

andPkthat of the city rankedkth. The steep-

ness of the relationship between size and rank

is incorporated by raisingkto the powerb;

that is,kb. No convincing explanations for

the rule’s existence have been developed, how-

ever, nor for variations in the parameterb

between regions (e.g. why the fifth-largest city

is smaller, relative to the largest, in some

places than it is elsewhere). rj

Suggested reading

Carroll (1982).

raster Raster is a GIS data structure akin to

placing a regular grid over a study region and

representing the geographical feature found in

each grid cell numerically: for example, 1¼

podsol, 2¼clay and so on. Rasters are asso-

ciated withremote sensing, image processing

and dynamic modelling, and are easily mani-

pulated using map algebra (e.g. multiplying

geographically corresponding cell values in

two or more datasets) and neighbourhood

functions (e.g. returning the sum of values in

3 3 cell window). Rasters are simple but often

voluminous. Patterns in the data are therefore

compressed using run length encoding,quad-

treesor wavelets. rh

Suggested reading

DeMers (2001).

rational choice theory Anormative the-

oryof individualdecision-making, claiming

that human action is motivated by getting the

most for the least. On the one hand, individ-

uals strive to achieve an unlimited set of ends

where each end is associated with a different

level of satisfaction or utility, but, on the other

hand, they possess only a limited means to

realize those ends. The role of the rationality

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RANK-SIZE RULE