The elements of the innate immune system are dendritic cells, macrophages, neutrophils, mast cells, eosinophils, basophils, and natural killer cells. The adaptive immune system has two basic elements, the B and T cells.

The human body rarely has serious reactions against antigens which are not harmful. However, the body responds to harmful substances with the bodily defense system. We can think of the situation like this: imagine that a man visits a certain country and enjoys himself. If he begins to cause harm to that country and its citizens, he will be arrested by the security forces of that country. The human body reacts similarly to unwanted visitors. Invasive substances that cause a defensive response are called immunogens. Disease causing germs are made up of structures such as fats, carbohydrates, proteins, DNA, and RNA. As cells of the immune system attack the organic structures of germs, the strongest reactions happen against the proteins of complex structures. The question is: how does the body recognize these harmful molecules and organic structures?

Different elements of the immune system recognize pathogens through different ways and means. The different elements are equipped with specific receptors, which enable them to work together as a defensive unit. These receptors can be compared to locks, alarms, and other controls used to protect a house. They make it possible to alert the body to most unwelcome visitors. The innately granted immune system has many different ways of recognizing aliens. These include the killer-activation and killer-inhibition receptors, the complementary system, and Fc receptors.

Natural receptors of the immunity system

People are born equipped with the innately granted immune mechanisms. These loyal and dutiful elements quickly recognize and respond to pathogens. If we continue thinking of the structures formed by the immune system as a key and lock, then the lock can be defined as the receptors of the innate defense system. Once this mechanism is ready, different signals given to the core of the cell trigger the release of certain molecules (cytokine and chemokine). Similar to cannonballs punching holes in castle walls, these molecules upset the membranes of germs. Thus the process of eliminating harmful pathogens begins. If it is not possible to handle the situation in a short time, the defensive cells call other elements of the defense system to help. Sometimes, natural killer cells and eosinophils take charge. The defensive line works in total cooperation. The key and lock relation constitutes the beginning of this defensive line.

Toll-like receptors won the Nobel Prize

Toll-like receptors have an interesting story. A German scientist spotted a certain gene found in drosophila (the vinegar fly) and named it “toll” (meaning great, fantastic, or stunning in German). Later on, since the structure and placement of nucleotides are similar to the “toll” gene, the newly discovered immune system receptors were named toll-like receptors. The scientists who made this discovery won the 1995 Noble Prize in medicine.

These receptors, found in the membranes of defensive cells, are responsible for recognizing and capturing germs. There are 13 types of defined TLRs in the human defense system. While some TLRs (TLR 3, 7, 8, and 9) are found inside the cells and arrest the harmful intruders, some are found in the cell walls and function like guards patrolling a border. By means of these guards in the cell walls, germs are spotted so other elements can eliminate them. These dutiful guards fulfill the duty they are created for – and they do it in a wonderful fashion.

Killer-activated receptors

Harmful intruders, such as viruses and parasites, sometimes invade the body’s cells. Some germs continue their lives by using the genetic material, metabolism and energy of the cells they invade. Moreover, they continue their expansion to healthy cells. If they expand enough, they can threaten the entire body.

As part of the body’s defense system, molecules signifying stress appear on the surfaces of these invaded cells, a sort of “warning” that the cell is occupied. In such a case, the killer-activated receptors recognize the cells with stress molecules on their surfaces and connect to them. Then a necessary sacrifice is made: the “occupied” cells are eliminated to prevent the germs from expanding to the rest of the body.

Killer-inhibitor receptors

All cells with a nucleus possess the tissue conformity complex known as MHC-I, which can be compared to an ID card, which shows a certain cell to be a healthy piece of the body. When some cells are invaded by germs, or lose their qualities due to reasons like cancer, they cannot show their IDs anymore. Namely, MHC-I is either too weak or is not seen on the cell’s surface. Killer-activated receptors, which are constantly on patrol, demand every kind of cell to show its ID in order to verify there are no alien invasions. The MHC-I identity of a cell is recognized and controlled by the killing-inhibitor receptors—or the bar code readers—of the natural killer cells. At this control, the cells that fail to show their ID card are accepted as invaded or as having contracted cancer. The cells in such condition are eliminated by the natural killer cells for the health and continuity of the entire body.

Complement system receptors

After entering the body, many viruses can reach different parts of the body by joining the bloodstream. In addition, blood also contains the harmful substances of any disease-causing elements dissolved in it. In order to recognize these harmful elements and toxic substances, a special defense team (the complement system) is assigned to the task. Many molecules in the protein structure take part in the complement system. By means of this system, the body recognizes and eliminates the potential threats which pass through the body’s physical, chemical, and biological barriers, and which might reach all the body’s cells via the blood stream.

This defense system is an interconnected and cooperative one. In situations like the deficiency of the elements that make up this system, the body is not properly defended and suffers from different diseases. The pioneering element of the complement defense system, known as C3b, binds to the lipopolysaccharide molecules on the membranes of microorganisms and triggers the complement system’s reaction. As a result of this reaction, the other elements of the defense team (C6, C7, C8, and C5b) are activated and embedded in the cell membrane of the microorganisms. By opening holes in the membrane, they cause the microorganism to die.

The design of our immune system shows how perfectly equipped humanity is for life on this planet. Though we consciously protect our homes and property, we never think about what is happening inside our bodies. If somehow we were supposed to consciously take care of these defensive processes, we would never be able to have “inner peace.” Thankfully, we are not alone.

Project Phoenix, launched by NASA in 1992, is an effort to pick up artificial radio signals from space; the project is also known as SETI-search for extraterrestrial intelligence. Davies does give some historical and technical information about SETI in this book. However, most of it is taken up with (a) arguments for and against the expectation that there are life-forms somewhere else than earth; and (b) discussion of how our worldviews would be affected by the discovery of alien intelligence or alien life.

The book is preceded by a long text from De Rerum Natura by Lucretius who, along with many ancients, believed that neither earth nor life upon it are unique. All beings belong to a kind; they come into being as the result of random associations of free-moving atoms. Therefore: life on earth must be one of a kind; the universal stuff of existence must have associated itself into other living forms.

Believers have also proposed existences in other realms. Why would God have created so many other worlds if they are uninhabited? Could the infinite majesty of God be content with the worship of only the conscious inhabitants of the earth? A Muslim thinker of this century argued that celestial bodies may be the dwellings or vehicles of angels and other spirit beings fulfilling God s commands and glorifying Him.

Would extra-terrestrial life be like the terrestrial one we know? The panspermia theory (pp.13-14) holds that the ‘seeds of life’ were blown about in space after the ‘big bang,’ landing here and there, and successfully on earth. Subsequent bombardments by inter-stellar material could also carry these ‘seeds’ around the universe. Thus, potential for life may lie buried belo

Davies regards science-fictional accounts of aliens as re-workings, in contemporary terms, of the supernatural beings that feature in the religious and pseudo-religious heritage of most human societies. That heritage is fiction undisciplined by reference to what is really, objectively, in the world. Scientific speculation, on the other hand, Davies regards as a quest for the reality independent of humans, waiting to be discovered by them. The laws of physics are not fictions; they are statements in the language of mathematics, as exact as we can make them, of what really is there. Do these laws require that there should be, or only that there could be, life-forms elsewhere than on earth? Alternatively, do they tell us that life on earth is an incident so utterly improbable that, even with billions of light-years and possible locations, no amount of re-shuffling of molecules could ever result in another, similar incident?

Attempts to tackle these questions turn upon our general worldview of what life is. Davies gives some attention to three such worldviews: (i) [life] was a miracle; (ii) it was stupendously improbable accident; and (iii) it was an inevitable consequence of the outworking of the laws of physics and chemistry, given the right conditions (p.15). He favours the third position on the basis of three philosophical principles: uniformity-the laws of nature are the same everywhere; they produced life on earth, they can do so elsewhere; plenitude-what can exist according to the laws of nature will exist, given the right conditions. For example, if physicists are able to describe the existence of a certain sort of particle within a mathematical scheme, they will (and do) find it to actually exist; mediocrity (or the Copernican principle, supportive of uniformity) the earth enjoys no privileged status; it is a typical planet in a typical star system in a typical galaxy.

The discovery of an alien microbe with chemistry different from ours would demolish, Davies thinks, the view that life is an accident. Life (already improbable) could not happen twice within the portion of the universe visible from earth (an immense region but finite owing to the constraint of the speed of light). Similarly, he argues, the view of life as a Divine miracle which privileges the earth and its human inhabitants, would be demolished. If, however, the alien microbe shared enough features of earth chemistry, both these views could survive: believers would invoke the unquestionable omnipotence of God and non-believers some version of the panspermia theory.

Davies devotes a whole chapter (pp.41-58) to the anthropic principle. This principle is in effect a version, palatable to modern scientific culture, of the argument for design. It holds that the universe runs according to specific laws and values (the so-called constants in nature) whose outcome is human consciousness capable of decoding those specific laws. Just any laws of nature will not result in conscious life; only these actual laws of this actual universe. Rigorously argued, the anthropic principle denies the possibility of conscious life elsewhere in the universe.

Diverging from the anthropic argument, Davies proposes that the coming-to-be of consciousness is a general law of nature-not a law expressible mathematically, nevertheless a real, reliable propensity. Consciousness is an emergent phenomenon. He explains by analogy: individual water molecules are not ‘wet’; the property of ‘wetness’ is a real, emergent phenomenon that comes-to-be from the association of water molecules. The observed tendency in nature towards increasing complexity emerges in life which, with more of the same increasing complexity, emerges in consciousness.

Davies is at pains to stress that he does not claim that the universe exists for human beings, only that they belong to it and it to them. He is glad to restore to human beings not a position of unique privilege but one of significance. The universe is a process of cosmic self-awareness; therefore, the emergence of consciousness elsewhere than on earth is to be expected to happen, not randomly, but as something really probable given conditions in which the laws of nature can operate.

Believers may find this conclusion comfortingly like the often-repeated saying that God is a hidden treasure that longed to be known; His coming-to-be known is the reason that existence exists. But Davies is not seeking, nor expressing, any religious sentiment-unless the plea for ‘significance’ is reckoned a religious aspiration. His argument relates to only that part of human consciousness manifested in modem-scientific curiosity about the structures of the material universe.

But human consciousness is more and other than this. It belongs to the inwardness of individual life, shaped by its experiences and reflections, of which the quest for scientific laws is (by volume) an almost negligibly small fragment. Further, consciousness is experienced by each person from within as responsibility, as questioning and answering about what he or she wills to do. This responsibility is more familiarly known as conscience. Its quest is not for scientific knowledge only but for value generally, and moral value in particular. Just as the language of science (i.e. descriptive language) is a very small part of the full potential of human language, so too the consciousness which Davies describes as an emergent property of intelligent life is a very small part of full human consciousness.

The Qur’an criticizes those who want the issue of their lives settled once-for-all after they have said that they believe or do not believe. They fear the trials of experience and thought, action and imagination, through which their individual will to achieve value is proven. All religions have a cosmology, a view of how the universe came to be. But the objective of this cosmology (certainly in the Qur’an) is not to equip human beings with intellectual power in the universe but to locate them (individually) with a purpose and meaningfulness within it. That purpose and meaningfulness are, in Davies’ sense, emergent qualities, and their emergence depends emphatically on the will to achieve value as well as the will to achieve knowledge-the latter being best addressed as a part of the former. Our mortality guarantees the suspensefulness of the search for value, and challenges us to believe that there is a yet higher consciousness, a further emergence, elsewhere than in this earthly life.

God is left out of modem-scientific speculation. Recourse to the concept of Divine Will is unhelpful for knowledge about the operations of the universe if, as is the case, knowledge is defined as a predictive (then manipulative) power to intervene in those operations. That definition of knowledge is simply inadequate to what human beings come to know of themselves and of there being a world to know themselves in.

Because scientific knowledge is too narrowly conceived, it may be that SETI scientists will no more recognize the communications of aliens than we can ordinarily recognize the presence of angels. By Divine permission, angels or spirit beings can make themselves known to humans-in visions of some kind. No doubt, with the same permission, aliens too, if they exist, can make themselves known to us. Project Phoenix could be rather an expensive way to be waiting for such a miracle.