Inordertograspageneralprinciplebyhandlinganinstanceofthatprinciple,? 'sworldofpureideas,? Forexample,howcanwedistinguish “threeness” fromthreeapples,theideaofserendipityfromaserendipitousevent,orasinGickandHolyoak's (1980) casetheideaofsimultaneouslyconvergingpathsfromdestroyingatumorinthestomachbyradiation?
AsIhaveargued,inrelationtotheGreenoetal.(1993) andLobatoandSiebert (2002) studies,discernmentorseparationcanhardlycomeaboutbyfocusingononeinstanceonly,inwhichthegeneralandthespecificarecompletelyinter-twined;theformerimplicit,,whatiscommon (theprinciple) maypossiblybediscernedfromwhatisdifferent (theinstances).Themoredifferentcasesavailabletothelearner,thegreaterthelikelihoodthattheprinciplewillbediscernedastheprimary,oronly,thingcommontoall,becauseofthelikelihoodofrulingoutwhatisdifferent (Reeves ＆ Weisberg,1994).Thelikelihoodofdistinguishingtheprincipleanditsspecificinstantiationcanalsobeenhancedbydrawinglearners' attentiontothecommonalitiesbetweenthedifferentinstances.
