Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
perspĭcācĭtas, ātis, f. [perspicax], sharp-sightedness, discernment, discrimination: qui nullā perspicacitate, sine innocentium sontiumque differentiā, … damnarunt, Amm. 15, 3, 2; cf.: perspicacitas, τὸ συνοπτικόν, Gloss. Lab.