From the introduction of one of Ghazali’s tracts against the Isma’ilis, entitled Qawāṣim al-bāṭiniyya (ed. Ahmed Ates, in Ilahiyet Fakultesi Dergisi, Ankara: 1954), p. 34 (my translation):
The sum total of the sophistry of the bāṭiniyya and their insidiousness is their argument that: disagreement (al-khilāf) obtains. And cognition of truth is either [through] reason (ra ͗y) or teaching (ta ͑līm) – and this is an issue about which [one must] reflect (naẓar). But a theoretical issue (mas ͗ala naẓariyya) has truth and falsity; and the sign of truth is unity, while the sign of falsity is multiplicity. And unity is in the doctrine of [those maintaining] ta ͑līm, while multiplicity is in the followers of reason and intellects. And if creatures in the diversity of their classes were to assemble together in resigning to [the doctrine of] ta ͑līm, the disagreements between them would be eliminated, diversity wouldn’t be conceivable in them, and their path would no doubt be [one of] unity. But those who occupy themselves with reason and intellects have disagreed in major ways; multiplicity and divergence being inevitable (ḍarūrī) among the followers of reason and intellects. And [the bāṭiniyya] maintain that the proof that unity is a sign of truth is that if it’s said ‘how much is 5 and 5?’ the right answer is that ‘it is 10’. And this response is one, no multiplicity in it. As for falsity, it is to say ‘9’ or ‘30’ or ‘a 100’ or ‘6’ or whatever you wish from among that which has no limit. Multiplicity is always on the side of falsity, while unity on the side of truth. This, then, is the utmost limit of their deception (talbīs).