that the oilstone is not harmful is correct.
sent1: the sparid is fissionable thing that does not wax. sent2: if the sparid is a mediastinum and a Coniogramme then the burgomaster is not a briefs. sent3: the oilstone is a kind of a Coniogramme if the burgomaster is a mediastinum. sent4: something is a mediastinum if it is fissionable and it is not a waxing. sent5: the sparid is a Coniogramme. sent6: something is not a mediastinum if it is not a briefs and/or it is fictional. sent7: the oilstone is not harmful but it is fictional if the burgomaster is not fictional. sent8: if the fact that the burgomaster is not harmful is not false the letterman is fictional and it surmounts. sent9: if something is not a mediastinum then it is not a waxing and it is a Coniogramme.
sent4 -> int1: the sparid is a mediastinum if it is non-nonfissionable thing that does not wax.; int1 & sent1 -> int2: the sparid is a mediastinum.; int2 & sent5 -> int3: the sparid is a mediastinum and it is a kind of a Coniogramme.; int3 & sent2 -> int4: the burgomaster does not brief.;
that the oilstone is harmful is not false.
$hypothesis$ = that the oilstone is not harmful is correct. ; $context$ = sent1: the sparid is fissionable thing that does not wax. sent2: if the sparid is a mediastinum and a Coniogramme then the burgomaster is not a briefs. sent3: the oilstone is a kind of a Coniogramme if the burgomaster is a mediastinum. sent4: something is a mediastinum if it is fissionable and it is not a waxing. sent5: the sparid is a Coniogramme. sent6: something is not a mediastinum if it is not a briefs and/or it is fictional. sent7: the oilstone is not harmful but it is fictional if the burgomaster is not fictional. sent8: if the fact that the burgomaster is not harmful is not false the letterman is fictional and it surmounts. sent9: if something is not a mediastinum then it is not a waxing and it is a Coniogramme. ; $proof$ = 
sent4 -> int1: the sparid is a mediastinum if it is non-nonfissionable thing that does not wax.; int1 & sent1 -> int2: the sparid is a mediastinum.; int2 & sent5 -> int3: the sparid is a mediastinum and it is a kind of a Coniogramme.; int3 & sent2 -> int4: the burgomaster does not brief.; __UNKNOWN__