先天功(gong)(gong),武俠小說中(zhong)(zhong)(zhong)絕學(xue)。《射雕英雄傳(chuan)》中(zhong)(zhong)(zhong)是(shi)「中(zhong)(zhong)(zhong)神(shen)通」王重(zhong)陽的(de)絕學(xue)。而(er)其他書中(zhong)(zhong)(zhong)解釋為呼(hu)吸吐(tu)納的(de)練(lian)功(gong)(gong)之(zhi)法,講究(jiu)抱元守(shou)一,欲練(lian)此(ci)功(gong)(gong),身如(ru)處子,不動(dong)如(ru)山,動(dong)如(ru)脫兔,呼(hu)先天下(xia)之(zhi)憂而(er)憂,后(hou)天下(xia)之(zhi)樂而(er)樂。修真活計有何憑,心(xin)死(si)群情今不生。精(jing)氣充盈(ying)功(gong)(gong)行具(ju),靈光照耀滿神(shen)京,秘語師傳(chuan)悟本初,來(lai)時(shi)無(wu)欠(qian)去(qu)無(wu)余。神(shen)則(ze)守(shou),身則(ze)守(shou),此(ci)功(gong)(gong)乃道(dao)家獨(du)門不傳(chuan)之(zhi)秘,以(yi)祛百病、調虛(xu)實,治(zhi)療沉重(zhong)內(nei)傷。此(ci)功(gong)(gong)極(ji)(ji)耗內(nei)力,需(xu)以(yi)高深內(nei)功(gong)(gong)為輔方可(ke)學(xue)之(zhi),當達于極(ji)(ji)限(xian)(xian)時(shi),能(neng)相(xiang)觸無(wu)聲(sheng),空(kong)中(zhong)(zhong)(zhong)暗勁(jing)橫流(liu),風力激蕩,功(gong)(gong)法里的(de)奧秘能(neng)使(shi)人潛(qian)能(neng)意(yi)識被(bei)激發到極(ji)(ji)限(xian)(xian),武學(xue)自會(hui)步入深不可(ke)測(ce)之(zhi)化(hua)境。
在金庸(yong)最(zui)初的(de)(de)小說(shuo)創作(zuo)中,「先(xian)(xian)天(tian)(tian)功(gong)(gong)(gong)」是(shi)(shi)「南帝」段智興(xing)的(de)(de)絕(jue)學(xue)(xue),而「中神通(tong)」王(wang)(wang)重(zhong)陽(yang)(yang)(yang)(yang)(yang)的(de)(de)絕(jue)學(xue)(xue)卻(que)是(shi)(shi)「一(yi)陽(yang)(yang)(yang)(yang)(yang)指」。后來創作(zuo)《天(tian)(tian)龍(long)八部》將「一(yi)陽(yang)(yang)(yang)(yang)(yang)指」改成「大理段氏」武學(xue)(xue)。因此,在修訂時(shi)《射雕(diao)英雄傳》、《神雕(diao)俠侶》、《倚天(tian)(tian)屠龍(long)記》、《天(tian)(tian)龍(long)八部》這(zhe)四部小說(shuo)時(shi),為(wei)了(le)能(neng)夠(gou)前(qian)後呼應,互相(xiang)對(dui)照,特意將王(wang)(wang)重(zhong)陽(yang)(yang)(yang)(yang)(yang)與(yu)段智興(xing)的(de)(de)絕(jue)技交(jiao)換,曾打敗(bai)「西毒(du)」歐(ou)(ou)陽(yang)(yang)(yang)(yang)(yang)鋒的(de)(de)王(wang)(wang)重(zhong)陽(yang)(yang)(yang)(yang)(yang)傳之以(yi)法,將「先(xian)(xian)天(tian)(tian)功(gong)(gong)(gong)」以(yi)「一(yi)陽(yang)(yang)(yang)(yang)(yang)指」使出,以(yi)剋制(zhi)「蛤蟆功(gong)(gong)(gong)」,以(yi)免造(zao)成段智興(xing)在第一(yi)次(ci)「華山論劍」時(shi),身負(fu)能(neng)夠(gou)克制(zhi)「西毒(du)」歐(ou)(ou)陽(yang)(yang)(yang)(yang)(yang)鋒的(de)(de)武功(gong)(gong)(gong)卻(que)只(zhi)是(shi)(shi)與(yu)「西毒(du)」戰成平手的(de)(de)古怪結果(guo)。王(wang)(wang)重(zhong)陽(yang)(yang)(yang)(yang)(yang)徒弟(di)「全真七子」跟師弟(di)「老頑童」周伯通(tong)均(jun)未獲(huo)得(de)傳授,僅與(yu)「南帝」段智興(xing)交(jiao)換過「一(yi)陽(yang)(yang)(yang)(yang)(yang)指」,用(yong)意是(shi)(shi)要「南帝」擁有剋制(zhi)「西毒(du)」歐(ou)(ou)陽(yang)(yang)(yang)(yang)(yang)鋒之能(neng)。「先(xian)(xian)天(tian)(tian)功(gong)(gong)(gong)」配(pei)合(he)「一(yi)陽(yang)(yang)(yang)(yang)(yang)指」除了(le)可以(yi)完全對(dui)付歐(ou)(ou)陽(yang)(yang)(yang)(yang)(yang)鋒外,也可以(yi)祛百(bai)病、調虛實(shi),治療(liao)沉(chen)重(zhong)內(nei)傷。
在不(bu)(bu)同(tong)小說描(miao)述里有不(bu)(bu)同(tong)作(zuo)用(yong)(yong),上官鼎小說《沉(chen)沙谷》描(miao)述:「全(quan)(quan)(quan)真(zhen)教」和「少林(lin)派(pai)」是最敝帚自珍,天(tian)下所矚目的(de)(de)(de)(de)(de)就是「先天(tian)罡(gang)氣」。全(quan)(quan)(quan)真(zhen)與少林(lin)雖然(ran)在取勁上有柔(rou)剛之(zhi)別,但天(tian)下的(de)(de)(de)(de)(de)武(wu)學(xue)是萬變不(bu)(bu)離(li)其宗,而(er)以(yi)「人(ren)」為原則的(de)(de)(de)(de)(de)。況且,兩(liang)(liang)派(pai)的(de)(de)(de)(de)(de)「先天(tian)氣功」又是同(tong)屬一個范圍的(de)(de)(de)(de)(de)事(shi)物(wu)。許多「全(quan)(quan)(quan)真(zhen)派(pai)」的(de)(de)(de)(de)(de)功訣上不(bu)(bu)夠份量的(de)(de)(de)(de)(de)地(di)方,拿「少林(lin)心(xin)法」一加對照,便瞭然(ran)於(wu)胸了(le),而(er)相反(fan)(fan)的(de)(de)(de)(de)(de),「少林(lin)心(xin)法」的(de)(de)(de)(de)(de)缺點也可以(yi)用(yong)(yong)全(quan)(quan)(quan)真(zhen)之(zhi)長(chang)(chang)來補救(jiu)。少林(lin)和全(quan)(quan)(quan)真(zhen)佛道(dao)兩(liang)(liang)門(men)至高(gao)武(wu)學(xue)水乳交融,少林(lin)和全(quan)(quan)(quan)真(zhen)的(de)(de)(de)(de)(de)心(xin)法一旦合并,舉世無敵!使用(yong)(yong)者(zhe):陸介《長(chang)(chang)干行》描(miao)述:流(liu)落於(wu)關(guan)外「天(tian)池派(pai)」。當(dang)年(nian)「全(quan)(quan)(quan)真(zhen)教」仗以(yi)威攝(she)武(wu)林(lin),幾達(da)百馀年(nian)之(zhi)久(jiu),後來全(quan)(quan)(quan)真(zhen)沒落,這(zhe)種武(wu)功失(shi)傳,方有少林(lin)武(wu)當(dang)等派(pai)興起(qi),算起(qi)來,這(zhe)「先天(tian)功」正是武(wu)學(xue)之(zhi)源。當(dang)掌力(li)(li)達(da)於(wu)極(ji)限時,能(neng)相觸無聲,卻最易傷人(ren)內腑,這(zhe)種功夫,有個名(ming)稱(cheng)叫做「否極(ji)泰來」,正是物(wu)極(ji)必反(fan)(fan)的(de)(de)(de)(de)(de)道(dao)理,掌力(li)(li)能(neng)不(bu)(bu)聞一些(xie)聲響,空中暗勁橫流(liu),風(feng)力(li)(li)激(ji)蕩。使用(yong)(yong)者(zhe):「定天(tian)一戟」高(gao)戰。