In conclusion, we have identified at least two physical observables -the singlet-triplet gap and the electron affinity -which provide quantitative metrics that correlate with experimentalists' qualitative ideas about the stability of silylenes. While a high singlet-triplet gap is a well-known measure of molecular stability, a low or negative electron affinity is indicative of low electrophilicity or low susceptibility to nucleophilic attack. In addition, a lower ionization potential of the silicon-based lone pair should be related to reduced nucleophilicity. Both p-conjugation (especially with amino substituents) and p-complexation are comparably effective strategies that afford stable divalent silicon compounds.