先天(tian)功(gong),武俠小說中絕學(xue)。《射(she)雕英雄傳(chuan)》中是「中神(shen)通」王重(zhong)陽(yang)的絕學(xue)。而(er)(er)其他書(shu)中解(jie)釋(shi)為呼吸(xi)吐(tu)納(na)的練功(gong)之(zhi)法,講究抱元守一,欲練此功(gong),身如處子(zi),不(bu)(bu)(bu)動如山,動如脫兔(tu),呼先天(tian)下之(zhi)憂而(er)(er)憂,后(hou)天(tian)下之(zhi)樂(le)而(er)(er)樂(le)。修真活計有何憑,心死群情今(jin)不(bu)(bu)(bu)生(sheng)。精(jing)氣充盈功(gong)行具,靈光照耀滿神(shen)京,秘(mi)語師傳(chuan)悟本初,來時無欠去無余。神(shen)則守,身則守,此功(gong)乃道家獨門不(bu)(bu)(bu)傳(chuan)之(zhi)秘(mi),以(yi)(yi)祛百(bai)病、調虛實,治(zhi)療沉重(zhong)內傷。此功(gong)極(ji)耗內力(li),需以(yi)(yi)高深(shen)內功(gong)為輔方可學(xue)之(zhi),當達于極(ji)限時,能(neng)相觸無聲(sheng),空中暗勁橫(heng)流(liu),風力(li)激(ji)蕩,功(gong)法里的奧秘(mi)能(neng)使(shi)人潛能(neng)意(yi)識被(bei)激(ji)發到極(ji)限,武學(xue)自會(hui)步入深(shen)不(bu)(bu)(bu)可測之(zhi)化(hua)境。
在金庸最初(chu)的小說創作中,「先天(tian)功(gong)(gong)」是「南(nan)帝(di)」段(duan)(duan)(duan)智(zhi)(zhi)(zhi)(zhi)興(xing)的絕學,而「中神(shen)通(tong)」王(wang)重(zhong)(zhong)陽(yang)(yang)的絕學卻(que)是「一陽(yang)(yang)指(zhi)」。后(hou)來創作《天(tian)龍八(ba)部(bu)》將「一陽(yang)(yang)指(zhi)」改成「大理段(duan)(duan)(duan)氏(shi)」武學。因此,在修訂時《射雕英(ying)雄傳(chuan)》、《神(shen)雕俠侶》、《倚天(tian)屠龍記》、《天(tian)龍八(ba)部(bu)》這四部(bu)小說時,為(wei)了能夠前後呼(hu)應(ying),互相對照,特意將王(wang)重(zhong)(zhong)陽(yang)(yang)與段(duan)(duan)(duan)智(zhi)(zhi)(zhi)(zhi)興(xing)的絕技交(jiao)換,曾打敗(bai)「西毒(du)」歐(ou)陽(yang)(yang)鋒(feng)的王(wang)重(zhong)(zhong)陽(yang)(yang)傳(chuan)之(zhi)以(yi)(yi)法,將「先天(tian)功(gong)(gong)」以(yi)(yi)「一陽(yang)(yang)指(zhi)」使出,以(yi)(yi)剋制(zhi)「蛤(ha)蟆功(gong)(gong)」,以(yi)(yi)免造成段(duan)(duan)(duan)智(zhi)(zhi)(zhi)(zhi)興(xing)在第(di)一次「華山論劍」時,身(shen)負能夠克制(zhi)「西毒(du)」歐(ou)陽(yang)(yang)鋒(feng)的武功(gong)(gong)卻(que)只是與「西毒(du)」戰成平手的古怪(guai)結(jie)果。王(wang)重(zhong)(zhong)陽(yang)(yang)徒弟「全真(zhen)七子」跟師弟「老頑童(tong)」周伯通(tong)均未獲(huo)得傳(chuan)授,僅與「南(nan)帝(di)」段(duan)(duan)(duan)智(zhi)(zhi)(zhi)(zhi)興(xing)交(jiao)換過「一陽(yang)(yang)指(zhi)」,用意是要(yao)「南(nan)帝(di)」擁有剋制(zhi)「西毒(du)」歐(ou)陽(yang)(yang)鋒(feng)之(zhi)能。「先天(tian)功(gong)(gong)」配合「一陽(yang)(yang)指(zhi)」除了可以(yi)(yi)完全對付歐(ou)陽(yang)(yang)鋒(feng)外(wai),也可以(yi)(yi)祛百病、調虛實,治療沉(chen)重(zhong)(zhong)內傷(shang)。
在(zai)(zai)不同小說描(miao)述(shu)里有(you)不同作(zuo)用,上(shang)官鼎小說《沉(chen)沙谷》描(miao)述(shu):「全(quan)(quan)(quan)真(zhen)(zhen)教(jiao)」和(he)「少林(lin)(lin)(lin)派(pai)」是(shi)最敝帚自珍,天下所矚目的(de)(de)就(jiu)是(shi)「先(xian)天罡氣」。全(quan)(quan)(quan)真(zhen)(zhen)與少林(lin)(lin)(lin)雖然(ran)在(zai)(zai)取勁上(shang)有(you)柔剛之別,但天下的(de)(de)武(wu)(wu)學(xue)是(shi)萬變不離其宗,而以「人(ren)」為原則的(de)(de)。況且,兩(liang)派(pai)的(de)(de)「先(xian)天氣功(gong)」又是(shi)同屬一(yi)個范圍的(de)(de)事物。許多「全(quan)(quan)(quan)真(zhen)(zhen)派(pai)」的(de)(de)功(gong)訣上(shang)不夠(gou)份量的(de)(de)地方,拿「少林(lin)(lin)(lin)心(xin)(xin)法」一(yi)加對照(zhao),便瞭然(ran)於(wu)胸了,而相反的(de)(de),「少林(lin)(lin)(lin)心(xin)(xin)法」的(de)(de)缺點(dian)也可以用全(quan)(quan)(quan)真(zhen)(zhen)之長(chang)來補(bu)救(jiu)。少林(lin)(lin)(lin)和(he)全(quan)(quan)(quan)真(zhen)(zhen)佛道兩(liang)門至高武(wu)(wu)學(xue)水(shui)乳交(jiao)融,少林(lin)(lin)(lin)和(he)全(quan)(quan)(quan)真(zhen)(zhen)的(de)(de)心(xin)(xin)法一(yi)旦合并,舉世無(wu)敵!使(shi)用者:陸(lu)介《長(chang)干(gan)行(xing)》描(miao)述(shu):流落於(wu)關外「天池派(pai)」。當(dang)(dang)年「全(quan)(quan)(quan)真(zhen)(zhen)教(jiao)」仗以威攝武(wu)(wu)林(lin)(lin)(lin),幾達(da)百馀年之久,後來全(quan)(quan)(quan)真(zhen)(zhen)沒落,這種武(wu)(wu)功(gong)失傳,方有(you)少林(lin)(lin)(lin)武(wu)(wu)當(dang)(dang)等(deng)派(pai)興起(qi),算(suan)起(qi)來,這「先(xian)天功(gong)」正(zheng)是(shi)武(wu)(wu)學(xue)之源。當(dang)(dang)掌力達(da)於(wu)極(ji)限時,能相觸無(wu)聲,卻最易傷人(ren)內腑(fu),這種功(gong)夫,有(you)個名(ming)稱(cheng)叫做「否極(ji)泰來」,正(zheng)是(shi)物極(ji)必(bi)反的(de)(de)道理,掌力能不聞(wen)一(yi)些聲響,空中暗勁橫流,風力激蕩。使(shi)用者:「定(ding)天一(yi)戟」高戰。