Based on facts of adjectival concord in Standard Arabic, this article offers evidence that upward probing (i.e., the goal c-commands the probe) is permitted only if downward probing (i.e., where the probe c-commands the goal) does not result in valuing the probe's uninterpretable feature. Such a constraint on upward probing allows us to account for several intriguing observations in Arabic grammar, including the fact that an adjective can agree in number and gender with one nominal, but in definiteness with another nominal. Hence, on the one hand, this article lends support to Agree proposals according to which absence of a match in the c-command domain of an unvalued feature (uF) is not fatal to the derivation. On the other hand, it speaks against Agree proposals that do not license downward probing or view it as parasitic on upward probing.
