▁a ▁Har ley - David son ▁to ▁test ifying ▁before ▁the ▁U . S . ▁Senate ; ▁from ▁t ough ▁city ▁youth ▁to ▁distinguished ▁scholar ship ▁– ▁was ▁cut ▁short ▁at ▁the ▁age ▁of ▁ 4 2 , ▁with ▁ten ▁books ▁in ▁progress , ▁including ▁a ▁history ▁of ▁aer od ynamic ▁theory . ▁ ▁Works ▁Books ▁Pattern s ▁of ▁Disc overy : ▁An ▁In qu iry ▁into ▁the ▁Con cept ual ▁Found ations ▁of ▁Science . ▁Cambridge ▁University ▁Press , ▁ 1 9 5 8 . ▁. ▁The ▁Con cept ▁of ▁the ▁Pos it ron . ▁Cambridge ▁University ▁Press , ▁ 1 9 6 3 . ▁. ▁Per ception ▁and ▁Disc overy : ▁An ▁Introduction ▁to ▁Scient ific ▁In qu iry . ▁Fre eman , ▁Cooper ▁& ▁Co ., ▁ 1 9 6 9 ▁[ W ad sw orth , ▁ 1 9 7 0 ]. ▁. ▁Observ ation ▁and ▁Ex plan ation : ▁A ▁Guide ▁to ▁Philosoph y ▁of ▁Science . ▁( Har per ▁Ess ays ▁in ▁Philosoph y ) ▁Har per ▁& ▁Row , ▁ 1 9 7 1 . ▁. ▁What ▁I ▁Do ▁Not ▁Bel ieve ▁and ▁Other ▁Ess ays , ▁( T oul min / W ool f , ▁ed s ). ▁Syn th ese ▁Library , ▁D . ▁Re idel , ▁ 1 9 7 1 . ▁. ▁Const ell ations ▁and ▁Con ject ures , ▁( H umph re ys , ▁ed ). ▁D . ▁Re idel , ▁ 1 9 7 3 . ▁. ▁Other ▁media