本文目的在觀察小五學生透過網路所進行的實務推理，藉以探究教師引導對學生產生推理之成效以及學生在推理過程中捷思的表現與涉及到之思考層次。本文發現如下：1.教師須適時給予學生實務推理之引導，其中可透過提問去引導學生在相關之問題情境中發展五段式推理捷思之思考。而教師之引導能幫助學生創造實務推理之經驗。2.五段式捷思是可用的，學生在推理中會發展這些思考過程，但其所涉及到之捷思是不同的；其中每一段並非必要發生，亦可能重複出現，故呈現的捷思可能是跳躍式或來回移動的。學生思考過程相關到「分析」的子技能較多，其反應學生大多習慣作「基本的思考」。好的推理者發表次數較多，亦傾向作「證實」之「批判性思考」及「反射」之「創造性思考」。而學生在非數學思考過程中之推理大多傾向個人對問題之價值觀。3.驗證推理中基本的、批判性與創造性三種思考層次存在的關係與階級；為了表示此三種思考的領域大小、各自獨立、互相含涉以及層次的階級關係，研究者修正了文獻中有關推理內涵的圖形。

The purpose of this paper was to observe fifth graders' practical reasoning which was executed under teacher's guidance through internet context. The effect of teachers' guidance was investigated when students were working on reasoning. Especially, students' heuristics and thinking levels were analyzed at the very instance of students' practical reasoning. The findings were follows. 1. The timely guidance of the teachers was necessary for students. Through question strategy the teachers could guide students to develop five-step reasoning heuristics in related situation. Teachers' guidance could create the students' experience of practical reasoning. 2. The five-step heuristic model was workable. The students could develop these thinking processes, but the involved heuristics com-ponents were different. Each step could be not to take place or could occur repeatedly. Thus heuristics students showed could skip some or shuttle back and forth among five categories. The students were used to acting on basic thinking because the subskills of “analyzing” took place more. The good reasoners were apt to “validate” about critical thinking and to “reflect” about creative thinking. The students' reasoning was mostly inclined to individuals' value for problems when their thinking pro-cesses confronted non-mathematics. 3. It was proved that there were the relation and hierarchy of three kinds of thinking contained in reasoning. The researcher revised the figure in the reasoning literature to indicate the fields, independence, intersection, and hierarchy among basic, critical, and creative thinking.