Hello Jun Yao: I think I am a good English Partner. I suppose I am a good English Partner. I think I can write fairly well. I suppose I can write fairly well. You may suppose that a Materialistic Philosophy is reasonable. You may think that a Materialistic Philosophy is reasonable. I do not suppose that a Materialistic Philosophy is reasonable. I do not think that a Materialistic Philosophy is reasonable. It may be your supposition that a Materialistic Philosophy is reasonable. It may be your thought that a Materialistic Philosophy. It would be an error for you to suppose that the Philosophy of Evidentialism is credible. It would be an error for you to thing that the Philosophy of Evidentialism is credible. (hope that helps)

at times can be interchangeable I suppose: probably better used in a conditional way I suppose if he could be convinced to wear warm clothes, he would be less likely to get sick so often. You could use I think also here I think that my son should choose a different college. You can say "I suppose my son should choose a different college" but the thought appears incomplete, thus "I think" is really the better choice here

From the Free Dictionary by Farlex, for SUPPOSE ================================================ sup•pose verb i. 1. to assume (something), as for the sake of argument: Suppose you won a million dollars in the lottery. 2. to consider (something) as a possibility or plan: Suppose we wait until tomorrow. 3. to believe or assume as true; take for granted. 4. to think or hold as an opinion: What do you suppose he will do? 5. to require logically; imply; presuppose. 6. (used in the passive) to expect or require (fol. by an infinitive verb): The machine is not supposed to make noise. She was supposed to meet me here. v.i. 7. to assume something; presume; think. [1275–1325; Middle English < Old French supposer=sup- sup- + poser to pose1; compare Medieval Latin suppōnere to suppose, Latin: to substitute, place below] .

I think I will go for a walk (making a decision) I think I will spend some money (making a decision) I think it is better to be polite ('I think' could be replaced by 'I believe') I think she is very rude. ('I think' could be replaced by 'I believe' I suppose we should give up the search. (I think could be used, but suppose is used as it is now 'inevitable') I suppose if he had been stronger he would have held on, (I think could be used here also) To summarise. 'I think' is more of a personal decision. 'I suppose' is more a reluctant decision made.

No they're not the same. "I suppose" is used in a sad way (showing that something affects you) and/or in more conclusive sentences. I think there's nothing else I can do. I suppose there's nothing else I can do. In the second sentence you're not accepting the probability that there's nothing else you can do all that well, you're sad about it, while in the first you're expressing your opinion about something that doesn't affect you. There's nothing else that can be done/ I think you're right. I suppose you're right. If you answer with "I think you're right" then you're expressing your opinion. If you answer with "I suppose you're right" then you're also expressing how you wish it could be different.