The objection identifies a real problem: some reports about the Quran's occasions of revelation and some legal hadith were transmitted late, disputed, or given polished chains by later transmitters. But this does not establish that the entire hadith and sira tradition was invented backward; it shows why reports must be graded individually rather than accepted as one undifferentiated body.
Why the objection is serious
Critics reasonably point to reports that connect an ambiguous verse to later communal controversies. Quran 5:67 says:
O Messenger, convey what has been revealed to you from your Lord. If you do not, then you have not conveyed His message. Allah will protect you from the people.
Quran 5:67
Some reports and later interpretations connect this to the Prophet's speech at Ghadir Khumm and Ali's authority. Other reports, including one attributed to Aisha, connect it with the Prophet's earlier concern for personal safety. Since the verse itself does not name either event, neither identification should be treated as certain merely because a report supplies a setting.
Schacht's observation also deserves a fair hearing: legal traditions can appear in fuller form in later sources, while their chains seem to become more complete as they approach the Prophet (PBUH). Fabricators did invent reports, and the Prophet (PBUH) warned:
Whoever tells a lie against me deliberately, let him take his place in Hell.
Sahih al-Bukhari; Sahih Muslim
The large number of reports circulating in the early centuries, and al-Bukhari's severe selection from them, confirms that Muslim scholars themselves knew the material required scrutiny.
What the evidence actually shows
It does not follow that a report first recorded in a later book was first created then. Early Muslims transmitted orally and in writing, and later books often preserve earlier teaching through several routes. The existence of early written material, such as the legal traditions associated with Malik's Muwatta and the hadith collection of Hammam ibn Munabbih, makes a simple model of ninth-century invention inadequate. It also matters that critics compare wording, legal usage, transmitters, regional traditions, and independent chains - not only whether a report appears in one early book.
Isnad criticism was not a late decoration added by Bukhari. Muslim scholars developed biographical evaluation, comparison of routes, scrutiny of hidden breaks, and criticism of wording. Modern scholarship has also shown that a chain may be assembled later without proving that its underlying report is wholly fictional; the chain and the content must be examined separately. Conversely, an apparently early chain is not automatically reliable.
What can responsibly be concluded
Occasions of revelation are often probable explanations, not Quranic facts. Reports about 5:67 must therefore be weighed, and the verse's general wording should not be forced into a sectarian conclusion. The existence of competing interpretations establishes uncertainty about particular contexts, not fabrication of all contexts.
Likewise, Schacht's thesis rightly exposed anachronism and prompted stricter historical testing, but a sweeping claim that hadith are merely back-projections goes beyond what the evidence proves. The sound position is neither credulity nor wholesale scepticism: accept what is firmly established, distinguish strong from weak reports, and leave uncertain historical details uncertain.