# Lesson I Before ink, there is only the hand and the sheet before it. Nothing more is needed. Practice is lost when the hand reaches past what is present. ## Try ```prolog ?- run([dup, swap, over]). true. ?- run([dup, made_up]). false. ``` ## Learn There is no parser--everything is deliberately expressed as ordinary Prolog terms. ```prolog word(dup). word(drop). word(swap). word(over). ``` A program is a list of known words, validated recursively. ```prolog run([]). run([Word|Words]) :- word(Word), run(Words). ``` [[00_index|Index]] | [[02_lesson|Next]]