The first and familiar remark is that every kind of thought is liable to be colored and modified in all manner of ways by our physical conditions and surroundings. We are not steam thinking-machines, working evenly at all times at the same rate, and turning out the same sort and quantity of work in the same given period, but rather more like windmills, subject to every breeze, and whirling our sails at one time with great impetus and velocity, and at another standing still, becalmed and ineffective. Sometimes it is our outer conditions which affect us, sometimes it is our own inner wheels which are clogged and refuse to rotate; but, from whatever cause it arises, the modification of our thoughts is often so great as to make us arrive at diametrically opposite conclusions on the same subject and with the same _data_ of thought, within an incredibly brief interval of time. Some years ago, the President of the British Association frankly answered objections to the consistency of his inaugural address by referring to the different aspects of the ultimate problems of theology in different “moods” of mind. When men of such eminence confess to “moods,” lesser mortals may avow their own mental oscillations without painful humiliation, and even put forward some claim to consistency if the vibrating needle of their convictions do not swing quite round the whole compass, and point at two o’clock to the existence of a Deity and a Life to come, and at six to a nebula for the origin, and a “streak of morning cloud” for the consummation of things. Possibly, also, the unscientific mind may claim some praise on the score of modesty if it delay for the moment to instruct mankind in either its two o’clock or its six o’clock creed, and wait till it has settled down for some few hours, weeks, or months, to any one definite opinion.