Is intercession permissible in Islam, especially within the Shafi'i school of thought?

Tawassul (seeking nearness to Allah) is of two types: permissible and forbidden. The permissible type is of three kinds: 1. Tawassul through Allah's names and attributes, as in His saying: "And to Allah belong the best names, so invoke Him by them," and "O you who have believed, fear Allah and seek means of nearness to Him." 2. Tawassul through righteous deeds, like the story of the Companions of the Cave. 3. Tawassul through the supplication of a righteous person during their lifetime, like the Hadith of the blind man who sought tawassul through the Prophet's supplication, not through his essence. The proof for this is that Umar (may Allah be pleased with him) sought tawassul through Al-Abbas, the Prophet's uncle, after the Prophet's passing. If seeking tawassul through his essence were intended, they would have sought tawassul through his essence after his death.

As for the forbidden type, it is of two kinds: 1. Innovated Tawassul: This is seeking tawassul through the essences of Prophets and righteous individuals, because worship is tawqifiyyah (dependent on divine textual evidence) and it is not permissible to innovate therein. 2. Shirk-associated Tawassul: This is directing acts of worship to other than Allah, such as supplication, slaughtering, and vows, with the aim of intercession, as Allah says about the polytheists: "We only worship them that they may bring us nearer to Allah in position," and "And they worship other than Allah that which neither harms them nor benefits them, and they say, 'These are our intercessors with Allah.'"