The New Organon Use of Form

Within Part 1 of The New Organon , Bacon makes it clear that some words are not necessary for completing or furthering the study of nature. Words like Quality and Action. However his use of Form becomes conflicted. On the 15th aphorism the words can be found and form is included with these and described these words "All are fantastical and ill defined"(New Organon Book One). Yet he continues to use form in later aphorisms in a supporting way. He didn't really address it and it was left to question why he thinks it 'Fantastical' yet still uses it as a valid word within his research and experiments. At one point in particular in book two he goes to show the investigation of forms, in this case heat. Basing whole aphorism on Forms of Heat, I feel he totally contradicts himself. That being said can form be seen as valid and appropriate rather than fantastical or ill defined word? I think yes he came into a conflict within this word and never decided to clarify that's why it didn't belong in the list in aphorism 15.