Asalaam alaikum
Ramadan Mubarak, eventhough its the 2nd week (can we ever seek too many blessings in Ramadan?).
I don't like getting into the halal vs. haram debates unless there is some intellectual or knowledge based benefit that may aid the believer in the future, insha Allah. In this case, and Allah knows best, but I believe there is some benefit in addressing this matter just as if we were brothers sitting around discussing this over dinner.
First, let us use the arabic word regarding intoxicants, khamr. 'Khamr' refers to any drink that intoxicates, so wine, beer, whiskey, vodka, cocktails, etc. This is known in the arabic.
Am Maidah (5):90-91.
Oh you who believe, Truly 'khamru' and gambling and divination by arrows are an abomination of Satan's doings: avoid it in order that you may be successful. Assuredly, Satan desires to sow enmity and hatred among you with 'khamru' and gambling, and to hinder you from the remembrance of Allah and from salat. Will you not then desist?
There are many ahadith addressing the prohibition of khamr. One includes: The Prophet (saaw) cursed ten categories of people saying:
Truly, Allah has cursed khamr, and the cursed the one who produced it, the one for whom it is produced, the one who drinks it, the one who serves it, the one who carries it, the one for whom it is carried, the one who sells it, the one who earns from the sale of it, the one who buys it, and the one for whom it is bought. (reported as sahih in Tirmidhi and Ibn Majah).
The illegality of any khamr, intoxicant, is prohibited. Qiyas extends this illegality to any known natural intoxicant, namely the common khat, marajuana, hashish. And this matter IS conclusive and Allah knows best.
As for cigarettes. It is true anything that is definitively harmful is haram. That is to say, to use something in a way that will bring haram to you is haram. Thus, to DRINK bleach is haram. Bleach will definitively erode the lining of your mouth, throat, stomach. It will definitively destroy your organs and if taken enough, will kill you. There is a direct causal relation between drinking bleach, or let's say a gallon of bleach and irreparably harming and even killing oneself. Drinking 6 oz.s of bleach is enough.
But smoking tobacco, or let's say smoking standard commercial cigerettes (cigz), since tobacco grows naturally and commercial cigerettes are chemically treated, is not definitively harmful and fatal as drinking bleach is. Commercial cigz are not directly tied to harm or cancer. That is to say, there is no medically definitive tie which rises to level which is as conclusive as drinking bleach is. As well, there are many many cases of people who smoke all their adult lives and do not necessarily suffer from cancer nor suffer harm from smoking. The same can never be said of drinking bleach. As well, the addictive nature of cigz do not necessarily render it haram being that cigz are not a khamr and nicotene is not a khamr. That is not to endorse cigz or smoking as a habit. Certainly not. But the stronger legal position is that smoking cigz do not rise to the level of haram.
So the question of definitiveness and conclusivity has to be held to a high standard and not surrendered or lowered to mere rhetorical or weak legal argument. That is not to protect people's bad habits, but to retain the high ideological standards and legal principles which have led the sharia`ah for 1400+ years.
May Allah forgive me for any misguidance and and misunderstanding and He is Allah, All Knowing, Wise.
Usama