From The Collaborative International Dictionary of English v.0.48 :
Capableness \Ca"pa*ble*ness\, n.
The quality or state of being capable; capability;
adequateness; competency.
[1913 Webster]
From WordNet (r) 3.0 (2006) :
capableness
n 1: an aptitude that may be developed [syn: capability,
capableness, potentiality] [ant: incapability,
incapableness]
2: the quality of being capable -- physically or intellectually
or legally; "he worked to the limits of his capability" [syn:
capability, capableness] [ant: incapability,
incapableness]