On the basis of a scaling hypothesis for the criticality of fluids, or fluid mixtures, held between parallel plates, we analyze the combined effects of finite wall separation and rsquo;rsquo;symmetry breakingrsquo;rsquo; boundary conditions at the walls (i.e., adsorption, or preferential adsorption of one component, at the surfaces). The resulting bulk (but rsquo;rsquo;twohyphen;dimensionalrsquo;rsquo;) critical point is shifted both in temperature and in density or composition (and in the conjugate field variables) by amounts described by scaling. The scaled form of the phase boundary is consistent with results from a low temperature Ising lattice gas model expansion.
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